[Discussion]Newbie apprehensive about possible issues

[repost due to automod deleting for not tagging the title]

Hi,

Wife and I are looking to get a dog. Pref something a couple of years old (we both work, so puppies just aren't a good fit). We're prepared to walk/jog before work and at night. Both work so close we'd be coming home for lunch, so dog would be alone for 4hrs at a time at most, Tues-Fri. We're definitely going to do training classes too, and I'd like to do clicker training. We have a townhouse with an unfenced yard. It's on a private drive so I'd feel safe playing fetch and what not as long as the dog isn't a jolter. But we also live really close to a dog park. Would be indoor dog of course.

Wife also works at a memory care place that'd let her bring the dog to work if it's certified companion animal, so if down the road the dog is trained and calm enough that'd be great. Not mandatory though.

So now to the real point of my post -- it seems all shelter dogs we see have some behavioral issues of some sort. We've both had dogs when growing up, but this'll be our first true dog ownership experience where we're responsible and what not. I want to make sure we don't wind up in a bad spot or letting a dog down etc. One thing I'm really scared of is separation anxiety -- how possible is this to overcome? How do we tell if it's so bad? What about a lack of socialization? One dog is great with other dogs, but scared/shy with new people. Apparently SUPER affectionate with the owners, but takes awhile to warm up to new people. Is this something freq. dog park visits and training might overcome?