You should also receive a preliminary title report that shows all liens and encumbrances and the terms of the auction and the purchase agreement should specify who is responsible for satisfying any liens.  

I have done some preliminary research on tax liens and read a book or to but I'm trying to figure out if 15k is enough to start investing in tax liens or would I just be wasting my time .

You can very likely get a preliminary read if you send in your financial information ahead of time.  

Get the contract with whoyou think is on title, the seller should tell you, give a copy to the title company and ask them for a preliminary search, that should be free if they are doing your closings.

I called a hml and got a preliminary approval.

If it is preliminary in order to talk to the seller about a purchase price, you can get by with simply the data in the form of schedule or you can also leaf through documents and bid Subject To your full due diligence.

You should at the very least have a preliminary title report pulled during the short sale.

However, the good thing that happened was it made me THINK about 'CREATIVE FINANCING', websites to do (PRELIMINARY) due diligence on properties, Fair Market Rents, etc.

Any quick and dirty techniques during preliminary screening?

$50000 is a VERY cheap rehab that's lipstick.Run a Clue report.In your contract choose the title company and opt to cancel when preliminary title report arrives and shows liens.Call your insurance agent to get a quote on a temporary policy.Are you the general contractor or who is?