A few tips:
1. When looking for a used vehicle, arm yourself with information about it before talking to the owner. Many owner's manual maintenance tables are available online. In this table are maintenance requirements regarding frequency of replacement of air/oil filters, engine oil, coolant, timing belts, etc.
1.1 Conduct a phone interview and ask if the items requiring replacement (based upon the vehicle's mileage) were replaced. Ask the owner if records and/or receipts were retained. Ask about the length of drives to work and back. Short trips of less than 3-5 miles may require more often oil/filter changes.
2. Salvage vehicles can save you quite a bit of money, but precautions should be taken.
2.1 Does the owner have photos of the damage? Rear damage is often preferred.
2.2 Was the damage professionally repaired. Are there receipts?
2.3 Take the vehicle to an auto body shop for inspection/integrity of repair. The underside should also be inspected.
2.4 A good-looking and well-repaired salvage title vehicle should sell for 40-50% less than a clean title vehicle, all other factors being the same (mileage, options, overall condition)
2.5 Keep in mind that ST vehicles can be more difficult to resell but if you plan to keep the vehicle for many years, you can save quite a bit of coin.
3. I bought a salvage title Mazda, 7 years ago and saved $8000 over a non-ST MX5. It has been super-reliable and I have enjoyed it, immensely over the years.