Is the Z4 something you can maintain yourself?

Depends on which one you are looking for, but I have a 3.0 Manual E85 I have had for close to 10 years and I do all my own work to it and it is super easy to work on. It's also been pretty bulletproof drive chainwise. It's at about 105K miles right now.

There's not really major problems with it or an excess cost over other options. The engines are reliable.

There are however a few quirks with the Z4, but they aren't bad. The most common is the electric roof motor failing. This has to do with how it's physically packaged in the car. There's some water ingress, and the motor gets wet. Over time, it rusts and fails. A new motor is $70 on eBay. There's window weatherstripping that rots in the sun, but this is also cheap and easy to replace. There's a coolant temp sensor that can fail, but again, it's a pretty easy fix and doesn't actually affect how it drives or even it actually reading coolant temp, lol.

Really, more of your experience will depend on past owners versus the car itself. How well or poorly it's been maintained is most of it.

The Maita, specifically the ND of the last few years with the updated engine and fixed transmission faults is a very good car. I really liked Mazda's choice in modifying the gear ratios and making 6th gear the 1:1 final drive. It basically creates a close ratio sport gearbox, and it's fun to row through the gears. The engine feels strong enough to move the car, but there isn't any wow factor otherwise. It's just good overall.

The Solstice, if you mean the GXP (the only one you should be looking at), or the Sky Redline, is a good car. For power, the turbo engine has good shove, and it's easy to make solid power. Handling is good too. The rear end suspension is...fidgety, and the car feels weirdly wide. It's also a lot of plastic and nothing all that attractive to look at inside. Storage is tiny too, especially with the top down since it takes away a lot of the trunk space.

The Z4 feels kind of like a big Miata. It's sort of the big brother in a sense. The key benefits is it's one of the only roomy sports cars. The other roomy sports car is the FT86/GR86, but you can't get a convertible. The Z4's styling and fit and finish is above others, and really only the ND Miata is somewhat close. The Z4 has solid power, especially in the 3.0L engine size or newer turbos. The only real competitor for power is the Solstice GXP/Sky Redline.

The only place I can ding the Z4 is on handling, and it's actually a fast car. Simply put, Mazda and Toyota/Subaru have made better handling cars when it comes to chassis dynamics, suspension, and actually pushing a car hard. Outside of an old and getting very expensive S2000, the ND Miata or the FT86/GR86 is on top for handling. The Z4 is good, in general, but it suffers the nature of BMW's choice in suspension design. BMW likes to use the bump stops as part of suspension design, and they generally lack bump travel. Compression damping is mild, and most of the work is done with rebound. In stock trim, the setup is so-so. You can drive fast, but it's not stable over bumps. This is similarly a problem with the Solstice/Sky choice too. The Z4 is fine enough for general use and fine enough for sports use. You can hussle the car fine. And you can always change the suspension if this is actually important for how you use the car. I've been in hobbyist motorsports for about 15 years, autocross and rallycross, and I'm kind of a stickler for suspension. I've always loved Mazda's setups, and the FT86 has been one of the best bone stock setups out there in decades. It's incredibly rare for an oem to set up a near neutral car stock, toss the keys to the customers, and say have fun oversteering. That just doesn't happen. Everything I've owned I've had to modify to dial in settings. The FT86 product has been the only one where I wouldn't touch a thing. It's that good, outside of maybe adding some camber so the tires wear even with mixed use. Stock, the Z4 is good enough to lean on and not worry much. It sticks well under throttle, and it's easy enough to manage. It's just not a stellar setup to rely on at 10/10ths. Almost no oem's stock setup is though.

The Z4 is a good mix of proportions. It's light and feels small around you. It doesn't feel oversized like a Solstice. Even though it's small, it's roomy and doesn't compromise like a Miata to be small. The Z4 doesn't skimp on power either to be a small sports car, so it remains quick. And even though it's small, it doesn't skimp on styling and quality of materials. The package as a whole isn't really one that any other option beats. On a whole, this thing is kind of king.

As for budget, I'll note you can look for a 3.0i instead of a 3.0si to save cost. Most, including myself wants to jump straight to the si. However, the 3.0i is the same engine just detuned and missing their variable intake part...which can be gotten from other models at a junk yard. You're just one part and a tune away from the si at thousands of dollars less. You also tend to see more pop up on the market than the si. The 2.5 is also the N52 engine, but I've never researched enough to see what makes that different from the 3.0i and 3.0si. I don't know if it's just detuned further or if there's additional hardware differences.

Also for budget, avoid the coupe. There's just a price premium on them, but I don't really understand why. Part of the attraction is top down driving, and the soft top is decent overall. You don't have a head room issue, it's quiet and insulated. It even barely takes up trunk space. Some may argue the coupe looks better, and in pictures, it kind of does. In reality, I've never disliked the roadster one bit.

My experience so far has been good with the car. I have a 2006 3.0i roadster, manual transmission. I am new to the car but spent some time researching and looking. I've also had the luxury of driving a lot of cars, including in actual sport use. I've autocrossed everything from a bone stock Honda Civic to a Dodge Viper. I'm also old enough to have driven cars from the 80s to today. The Z4, especially of this era with the old inline 6 is really a sweetheart of a car. It's fundamentally classic roadster and ticks all the right boxes. And you don't have to compromise for it. It's just a really good, lovely thing with all the charm and character you'd ever want, and it's interesting and engaging to drive.

As for pricing, just be patient. If you can afford yourself a couple months time, things pop up. If you're looking at the Solstice (again assuming GXP here because I don't think the normal car is worth it, really boring to drive relatively speaking), if you're in the GXP price range, then you are well within the price range of many Z4s popping up. I don't know what your range is though.

A note, the 2006 is the first year with the newer N52 engine. The previous years had the N54. The N52 is 200 lbs lighter and has more technology. However, the N54 was a tank of an engine. It's a good engine if you're looking to go forced induction, and it was used on the Z4 M car in this year range for this reason. And it's why the N54 was still used in the next generation for the 35i and 35is models. The N54 is a good engine for forced induction and power. You're kind of splitting between 2002 to 2005 and then 2006 to 2008, or for the 3.0si, only 2006 to 2008. The 2006 year also included a car refresh with styling and feature changes. For the most part, you're looking at 2006 to 2008, unless you are specifically looking for the N54 engine or specifically looking to step to pre-refresh for cost savings.

I have had my 2004 z4 3.0i for over 10 years. I've put 100k on it (141,000) I've done valve cover gasket twice, water pump twice, full front and rear suspension replacement, rear springs, and of course front/rear brakes, cooling system replacement too. The most I've spent to have a major repair was $500 for the oil pan gasket done. Get the right tools and knowledge off youtube and you'll be fine.

05 2.5i here with just under 135k on the clock. Have done most of the work myself over the past 8 years of owning and only recently took it to a shop I've done business with over the years so they could do the water pump/belt work because I had no space or time for it at the time. Can confirm these cars are easy to work on, and maintained are pretty much bulletproof.

I have an 07 3.0si auto(97k odom), and it's my first "real" car. I bought it with zero car knowledge, and a year into owning it(with the help of my extremely knowledgeable friends) I have yet to take it to a garage/dealer/shop. I've learned more than I ever could have imagined in the past year because of this car and I have yet to run into anything I couldn't do myself/ with assistance from a friend. From personal experience I would say yes, this car is definitely something you can maintain yourself if you have the ambition to.

You sound like me last fall. We ended up with a 2003 90k z4. I wouldn't be worried about the milage difference. The lower mileage means it has sat more and that can be as hard as being used. Being well maintained is the most important.

The BMWs do have their quirks compared to US brands. If its going to be a weekend type car you should be fine. I will say I wouldn't recommend it as a daily as it's not terribly practical.

This sub as a lot of good info. A few things I did deal with is swapping out an old set of run flats for standard tires and an inflator kit the CD player quit working so we got on of those cables to hook up an aux jack.

Parts can be a little spendy as it is an old European car. However bolts are still righty tighty lefty loosy.

Do not buy a Solstice. Either Z4 or Miata. You can maintain either 90% of the time

Definitely. I'm not a mechanic by any means but I did all maintenance myself for 7 years. I've had a 3.0i and Z4M, both were extremely reliable and easy to work on