. - My belief is variable rates such as most heloc are best for shorter term loans.  

Maybe in 10 years the fixed expenses, not even the variable ones, will outpac eht e rent. 

And there is actually a level at which your agi income makes a difference.Safe to say that $500K is going to cost you a minimum of $100K and possibly up to $200K depending on all of those variables. 

I still need to truly vet the area to make sure I'm comfortable living there and there are still the closing variables that are still open as of now. 

Contracts cannot & will never account for every possible variable one can encounter in life.

However,  there are many variables that come into play: location, low rents, Cap X costs, etc.

Which is profit driven and will always take the path of higher prices and more profit for those who control certain housing variables. 

We usually look at speculation as the furthest out variable for our investing, as we prioritize cash flow. 

And the answer is always the same :-) There is no way to accurately do this...too many variables and moving parts, plus it varies too much from one locale to another.You need to find a really good General Contractor and pay him to walk the property with you....over and over....until you feel really comfortable estimating yourself, and that should take years.Alternatively there are online calculators (even one here in the tools section) but I would not rely on them for the reasons listed above.

Both rental income and property valuation can be impacted by variables such as employment growth, population trends, and economic stability.Have a clear exit strategy.