., there are a total of 17 building systems, including, among others, plumbing, heating, fire escapes, elevators, kitchens, bathrooms, pointing or exterior surface repair) are completely replaced when the building is 80 percent vacant, units subject to rent stabilization can be deemed permanently exempt and converted to free market status.

It is a manufactured home on a permanent foundation.

Everything else is good though, on private lot and permanent foundation.

Even if I don’t move to Austin permanently, I’d like to have a place or few to stay or to offer family in the future.

That serves two purposes, it gives you a great surface to put the new product on (key factor in longevity) and will not permanently damage subfloor when you change flooring next time.

This way you have something a bit more permanent than renewing private lenders every few years. 

In our area if it has a permanent foundation you can use a regular home loan.  

Mortgages are fixed Rates but have higher costsWhat this means is that a HELOC is NOT designed to be a permanent financing solution.

I would certainly get prequalified from a lender on the permanent step to make sure you qualify for a loan like that (and that they have a loan that can actually lend on it). 

The savings account is for any "permanent" money - reserves, cashflow being saved for the next investment, etc.