I think professional photos (link removed by moderator) are the best marketing tool. These days it's all about the internet. Make sure you have a Realtor who syndticates fully to Realtracs, Realtor.com, Trulia, Zillow, Craiglist, YouTube, [link to her website deleted by Zillow moderator, please read Good Neighbor policy]
Assuming a loan is not common in today's market because interest rates are still at near-historic loans. And like Mike says, you can only have one FHA loan at a time. In order to qualify for a conventional loan on a new house, most lenders now require that you have at least 30% equity in the current home. Have you considered trying to short sale your current home? You'd take a hit on your credit and you wouldn't be able to purchase a new home for 2-3 years, but it may be a viable option for you to get out from underneath it.
I find it running at 3.5% to 4.5% these days. Closing costs vary depending on a number of criteria: bank fees, appraisals, origination fees, attorney fees, tax stamps, credit reports, tax escrow, insurance premiums, etc. The type of loan arrangement you choose is the most important factor. The best way to get a good estimate is to request a Good Faith Estimate from your lender.
Almost no REO owner will accept a "home sale contingency" as part of an offer to buy a foreclosure if the current home is still on the market. Some lenders might consider a contingency if you already have a contract on your current home but they're going to want full copies documenting that entire transaction. Where the down-payment comes from is of no importance to the REO holder. A strong pre-approval from a reputable letter ought to be justification enough. Buying a foreclosure really isn't that much different from buying a regular home. The steps you mentioned above usually aren't necessary. The biggest hurdle is realizing that the home will be sold AS-IS and praying that your appraiser doesn't require repairs.
Also, in general, any Realtor can show you any MLS listed foreclosure. I would encourage you to start a relationship with an agent who can show you homes and negotiate on your behalf. There is no additional fee for this. You might consider choosing an agent with experience in the foreclosure market. Buying a foreclosure is in some ways easier than buying a regular resale home, but youmust understand the process, benefits and pitfalls of buying a home that is sold AS-IS.
It is harder to negotiate new construction than resale homes or builder homes that are finished and in inventory. Most builders start out with a base price that is not really negotiable. Then they add costs for each upgrade you choose. The best tactic is to find out what the final cost will be including each upgrade you want. Then go back in a few days later and offer less. Of course with pre-construction you are also getting the colors you want as well as a builder warranty. Run the closed comps to see if other homes are falling the same price per foot in the neighborhood. Remember that a builder isn't going to construct something that they won't make a profit on. With the cost of gas so high right now, the cost of building will go up in tandum.
If you are still under your home inspection period, you can definitely back out and get your earnest money refunded. I recommend that you look over your contract carefully. The Tennessee Association of Realtors Purchase and Sale Agreement has very specific language regarding the timeframe of negotiation repairs. Make sure you stick to the calendar in the contract or you could end up in a situation where you can't back out.
How long will it take you to save the down-payment? Consider crafting an offer with a far out closing date, maybe 75-90 days out. To get the seller to seriously consider a delayed closing, you might make your earnest money deposit non-refundable. Don't forget to ask the seller to pay for closing costs (It sounds like you'll need the help). And ask your lender if you can make payments toward your earnest money/down-payment every week or two until you've saved enough. I've had a buyer successfully do this previously. I'm betting you tried to qualify with THDA and were disallowed based on income. Unfortunately that's the only closing assistance program know about in our area. USDA was mentioned earlier, but it is not going to be available in most parts of Davidson County.Do you have a Realtor who can help you craft an offer?
Have you considered a short sale? I'd estimate that 10%-20% of the homes I'm showing these days are short sales. It'll hurt your credit in the short term, but if you gotta go...
It really depends on how accurate the city tax appraisals are, and how much information Zillow has access to in your area. Also, if you live in a homogeneous or cookie cutter area, Zillow has a larger probability of getting it right (Think Cane Ridge or Providence in Mt. Juliet) Whereas if you lived in an older neighborhood with varying styles of architecture and different levels or renovation, it "zestimates" would tend to be a little more off (think East Nashville or Green Hills).