Given the current situation, you might also consider buying a stripped lower. Technically, that is the rifle, so whatever you put together later would hopefully be grandfathered in as pre-ban, if a ban actually passes (and I don't think one will pass). Of course, the prices on uppers have risen 3 fold in the past month.
Either hold out, and pray that nothing get's passed, or get what you can.
Even the low end rifles can be fixed with a little money (typically cost prohibitive) but if all you can find is a BM, RRA, Stag, Mossberg...replacing some parts, and having a gunsmith do some item specific work (gas key staking, reaming the chamber, replacing the FCG) you can get them a bit more reliable. Even if you find a used one with a worn out barrel, so long as the receivers are not trashed, you can re-barrel them for a couple hundred.
Beware of buying any used mags. Lots of people are selling off their bad mags now at double what new cost 2 months ago. Mags are a consumable item, especially any plastic ones.