Guessing by the questions you're asking, sounds like you're not using an agent. If you are, these would all be great questions for her/him.
First of all, 90 days is not a long day for a home to be on the market, in that price range. In fact, that's the norm. Since all Listing agents require that an offer is accompanied by a Loan letter, which means there is a pretty good chance the buyer is qualified, the only thing a seller has to gain, by accepting your cash offer, is about one mortgage payment. (of course, your agent will have to find the motivation for selling and I've found that many sellers agents give up way too much information.) Most resale properties are going for 96-97% of the asking price and that discount is disappearing. (not a lot of huge discounts in Austin, TX) In fact, if you submit a low ball offer, and a few of my clients can tell you this, recently, not only will the sellers perhaps ignore your offer, but you've just ensured that they will drag their feet, and the back and forth will cost you the home, as there's a pretty good chance someone will come in with a better offer. Remember, you're not under contract until both sides agree on a price and conditions. I'm not a "rose colored sunglasses" Realtor, but I assure you, that the market has turned a corner, i.e. multiple offers, etc. My broker just got a contract on a house, for full price, within 4 hours of being on the MLS!
Buy from a builder or a resale home? All depends on the motivations, again. Look at all the houses. Look at the comps. Buy the one you want after looking at all the data, and make an offer that supports the data. Know the supply of houses in a neighborhood, i.e. the absorption rate. That data alone, will tell you the market in your chosen area.
What you're looking for is about 60% of market value. Even foreclosures and short sales are priced at 85-90% of market value, so your expectation to pay 250K in a 350K neighborhood isn't likely. Nonetheless, best of luck!