About to buy a 1978 Honda 250

So I'm extremely new to dirt bikes and basically know nothing about them.

I've found a 1978 Honda 250 in good condition for 1300$ but I have no way of knowing if this is a smart decision or not.

This is going to be my first bike and so I was looking for something sub-1500 and this is pretty much all I've found in my area.

I'm totally cool getting an older bike, I think it looks pretty damn neat, but I wanna know if this is a bad decision considering the age. I have no idea how reliable finding parts will be and I don't wanna be stuck with a broken bike I can't fix.

I'm 20 140 lbs and I plan on really only trail riding with it.

Can someone help me with whether or not this is a bad idea and whether or not I should get a more modern bike.

Much appreciated and my apologies for the ignorance!