my friend got a univega frame converted to singlespeed, with a handbuilt rear wheel, and mostly new parts built up for $300. i considered this a good deal. this was at bikes not bombs in roxbury, ma. do yourself a favor, save your pennies, shop around, and keep an eye on craigslist.

for $150 potentially you could buy a bike, and convert the rear wheel to a suicide hub for the cost of a cog and some loctite. it's not entirely uncommon, but i wouldn't reccommend it to someone like yourself.