I'll second about the rims/wheels. At 255lbs, I warped the rear rim on a used 95 Trek 800 Sport (entry level, rigid mtb). Found a pair of Sun Rhyno Lite rims on ebay.... Bomb proof, as one of the reviews suggested. Five, plus, years later, I am still on these rims (now less than 175lbs).
That old bike and being near vegan have added at least 20 years to my life

Try craigslist, ebay and shopgoodwill.com for used bikes. Better to get strong, inexpensive steel and add stronger rims.