Your best teacher will be experience and that can't come from books and formulas. 

The formulas are all the same.

Pay the bill yourself, then reimburse yourself by charging the tenants based on a formula.

What is the formula to calculate what the business is worth based on gross and net STR income?

Quote from @David Martoyan: Has anyone here successfully adjusted their strategy to focus on finding deals that don’t follow the traditional ARV formula?

They have a formula based on the property and its features as well as the tenant's income and expenses. 

There is a formula that you must follow if you want to perform, having a realtor who knows the market inside and out and practices what they preach is an absolute necessity. 

I had clients in PHX  and Vegas that lost their 4 plex's because they went 100% vacant and stayed that way.. they owned 4 or 5 of them.. it only took about 3 months of negative cash flow and they were done.Max leverage loss tenants  lose property.. that's the formula..  

In fact the developers formula that I use to come up with a max offer that was taught to me by a very successful land developer is .4x(Sellout Market Value - Development & Selling Costs) Basically, it's 40 cents on the finished dollar less costs.  

This article is a good primer: https://www.sageregroup.com/the-secret-formula-to-getting-ri...