Newbie here, question anout Tax Deed in Texas

[Amber Matas]

Hi there! I have two rental properties I own in Southern Ca and recently relocated to Texas. I am thinking of making the leap and expanding into Tax Deeds through the county. My goal is to own the property and keep as a long term rental so it will be especially important to really vet the property. If it gets redeemed, then its a just  a little extra money to put back into investing.   I have been reading about the importance of thorough due diligence, and plan on attending a few auctions to get the lay of the land before doing anything. I know this is an area full of super experienced folks, many with deep pockets, so I am treading lightly.....

Was wondering if anyone could help clear up a few questions I have:

1. I have read that you must be careful because you could inadvertently (amongst many other things) be purchasing a deed on a second mortgage- can someone help explain this to me? For example, if I see that the property is from back property taxes- can that be still be on a second mortgage? I was under the impression that  on a mortgaged property the bank financing the mortgage would pay the back taxes before it would allow the forced sale. I would assume (I know, never assume, but while I am trying to learn & understand the process and before I go down to research a home's title) that the situation on something like this would mean the home is owned outright and the only other things that would come along with the Deed could superior liens (IRS, Child Support, etc.) and not a 1st mortgage.  Any input?

2. Title research- I plan on spending some time down at County Records and doing research to get the hang of it, but also employing the help of a professional title company if I am going to go with the intention of bidding on a property. Any tips on what to look for while doing my own research?

Thanks!