will repairs and or parts be expensive for a 90 SE sedan with 149k miles

Yes, 'fraid so. Everything is relative, "compared to what?" ....but when you start in on a 1990 M/B, depending on what it needs, make sure your Visa Card is paid off, you gonna need it. Again, "Compared to what?" if you asked the same question about a 1990 Lincoln Town Car w/150,000 miles I would say the same thing. The key here is what it needs and how much the asking price is. Don't worry about mpg, that is the least thing you need to be concerned with.

I agree with DavidH25...Also, this car, in my honest opinion, especially at 149,000 miles + over 20 years old will be your classic money pit. I would suggest that you do NOT buy it, unless you almost literally want to shovel big time $$$ into repairs and maintenance. 12 mpg kinda sucks too.

Thx you guys. Really appreciate the advice. Able to buy car for $900 but just wasn't confident about the maintenance that was or wasn't done. Rest of car is great, body, interior n all bells n whistles. But for how long. Again, appreciate your insight.