1. A good starting point is using the 1% rule when viewing any and all deals. This basically means that your expected monthly gross rent should be at least 1% of the sales price-talk to several different realtors and PM companies to get realistic expected rent. This will quickly eliminate a lot of houses. Once you have a handful of properties that meet the 1% rule, plug in your numbers into a proforma/APOD you are comfortable with. Make sure you account for vacancy loss, CapEx, Property Management, Insurance, Property Tax, Repairs & Maintenance, HOA if applicable, mortgage etc.
Learn about metrics such as Cash-on-Cash, ROI, Debt Coverage Ratio to help identify what makes a deal worth while.
Have you considered a 30-year mortgage? This would increase cash-flow.
If you are comfortable with it, look into investing in out-of-state properties with more favorable markets. You can read, Long-Distance Real Estate Investing by David Greene. Very informative.
2) I think a good launch point is to focus on class-B neighborhoods, this would be your mid-level housing. Look up demographics and housing statistics in your target area. I look for places with a favorable renter-to-owner ratios, low crime rates, good schools, etc.
3) Hire a realtor or locate a wholesaler with a good reputation. In the book previously mentioned, Greene mentions finding an investor-friendly realtor....essentially someone who invests in real estate too or understands what makes particularly houses attractive for investors. Although I am new to the RE world, I have learned through advice and research that its a lot easier to have someone else look for you. Let them know what you need. Build yourself a criteria and have them work off of it.
Hope this helps. There are a lot more people on here with much more experience than I have. Utilize the forums and constantly ask questions.