In the world of real estate, I faced many problems that put my strength and drive to the test.

I wouldn't do a rehab on this until the HELOC/credit cards/personal LOC is all paid off and you had around 35k reserves (put it in a HYSA if you want, it's what I do).

Several weeks after sale,  out of the blue I received a letter form a creditor that there was a lien for $600 on the property PRIOR to the sale, that the builder never paid and now they are going to put a lien on the property against my name.

They are always going to put the curtain outside the curb so water gets on the floor if you use a curtain in a shower only setup. 

We walked a model where it was nearly completed and the original buyer had decided to walk away, so the home was put back on the market at a $15,000 discount of the original list/contract price. 

not 10%... not 25%... more like a 75 or 100% increase from purchase price usually.and as others have said you don't want to buy it with a DSCR loan - you want to buy it with hard money / bridge money and then refinance into a DSCR loan.using a HELOC for the down payment just puts tremendous pressure on you to boost the value. 

Also easier to separate bank accounts etc You don't need to put the rental in an LLC.

Perfecting the property as an STR without putting too much money into decorations and amenities.

Another idea perhaps more leverage than anything would be the threat of a forced sale where OP would collect first every dollar put into for the property over the years before the pot is split. 

That's buying something for $50k-$60k and putting another $20k-$30k into rehab.