You also have the advantage of doing all your cap ex (capital expenditures) up front.

At least 2,600 victims invested their retirement savings, totaling about $400 million.Shapiro siphoned off $35 million for his own benefit, according to prosecutors, spending $3.1 million for chartering private planes and travel, $6.7 million on a home, $2.6 million on home improvements, $1.8 million on personal income taxes, $1.4 million for his ex-wife, and more than $672,000 on luxury automobiles.Roseman received $2.5 million for himself and Acevedo received $1.1 million, prosecutors said.The Securities and Exchange Commission’s previous enforcement action in 2017 was settled in January for a total of $1 billion in penalties and disgorgement of ill-gotten gains, the agency said.

The thing with STR's is the Op Ex line items and even revenue are fairly dynamic and will adjust based on your business model. 

When analyzing properties, is there a certain percentage of ARV that you can determine if its a good deal without doing the calculator on every property EX: ARV 300K (must get house for 225,000 without repairs)- 75 percent-  Is this right?

If you truly want to leverage all Cap-ex expenses, deferred maintenance and desire more consistent cash flow and have 20% down, then TK. 

Cap ex, vacancy, routine maintenances, taxes, insurance, landscaping/snow removal(depending on market) and whatever else you can throw at the numbers. 

Also learn the lingo and terminology i.e. cap rates/price to rent ratio, COCR, What are reasonable reserves for your market i.e. cap ex, vacancy, maintenance etc....

(Ex Parents with a low income visiting to see their son or daughter graduate) It is similar to an airbnb, but they provide free room and board. 

.- Vacancy (7%), Taxes (get actual #), Insurance (get a quote), Cap Ex and Repairs (15%), Property management (8%), Trash (get quote if needed), Landscaping (get quote).You can change them around as you see fit, i.e. it was just remodeled so there won't be as many repairs/cap ex.Good luck.

All other major cap ex expenses have been taken care of, has a newer bathroom, newer kitchen, electrical updated etc.As it sits it will likely appraise for 65k with a new roof.