Originally Posted by phoebeisis

The 1990's series 700-720 -730-750 (and occasionally another number or two-770 maybe 790)
are poor mans 29ers.
They are 700c-and will take a 2" wide tire I think,
They easily take a 40mm-with maybe 8mm clearance-so they should handle even a 50mm
Now 50mm are frequently a bit less wide than 50mm-maybe 45mm

In any case the 720 on are at least main tube cromo- 750 on DB full Cromo frames
They have appreciated a bit lately-but you should be able to get a 750 on ebay for maybe $225 delivered
Locally maybe $150 or so
Decent lower end Shimano components-21 speed-nice reliable sturdy treks

You can also buy a reynolds 853 frame-29er-just frame maybe fork-for maybe $250-$400-cost you another $300-$450 for components depending on your taste-