I have a good idea of my requirements for approving applicants, which I was already going to give to a prospective PM.

This will avoid needing to foreign qualify your out-of-state entity in the State you are buying the property in.However I am wondering, if I am forming an LLC, with the sole purpose of buying tax liens (I am a foreign national btw), and I don't wish to limit my tax liens acquisition in just 1 State, but instead buy tax liens all over the US..Do i need to foreign qualify my LLC in EVERY State I buy these liens in?

Yes the DST's can have some limits that might be prohibitive. 

Do most of your applicants have pets and do your competitors provide fences?

If you’re not looking for professional management that’s no problem but at least have one find a tenant, do the showings, marketing and screen applicants so you can be set up for success.

Within the city of Austin and other local markets with limited inventory, homes are spending a fraction of time on the market—as little as two weeks in some areas.

from my point of view if your an individual and not partnering with folks who ever is going to sue you is going to name you personally.. this is where you need good insurance to take up your defense as your first line of defense.whether they have the right to sue you is immaterial.. or whether they will prevail is immaterial.. if your operating as a group or partnership and have clean records this can limit your exposure to your ownership.other than that  retirement accounts should be maxed out they basically cant be touched... certain trusts.but just LLC labyrinths like you mention.. those are not going to do it for most or.. you will spend a ton of dough fighting to make the position they can't sue you. when suits happen everyone is named .. that's when you need good insurance to handle your defense.

The bad is that often times you will find less care is being taken with your property, the Section 8 has inspections, which at times can be obnoxious and often times you are renting to tenants with no job or limited employment, so they are home all the time, causing more wear on your house. 

I plan on putting them through a new application so that I have the experience and also all my i's dotted and my t's crossed.

Just my initial thoughts based on the limited information, I wish you the best with whatever you decide.