Many will let you refi sooner, but you will be limited to a percentage (typically 75-80%) of cost versus value. 

LLC financing will be at least a percentage point higher on the rate, and insurance will be a commercial policy, I.e. expensive.

He said that there has to be some percentage according to IRS tax law?  

I calculate the wattage used from each meter and use that as a percentage of the electric bill.  

Before it listed out almost every expense category and you could calculate them by a percentage.

Being in the oil business i understand the ins and outs of what an investor likes to see (returns and the awesome tax benefits with oil wells) plus i also understand how i can benefit from having the investor in the oil business with making money off the deal plus a percentage and monthly fees for operating expenses.

A good percentage of my clients are 1031 exchanging their short term rental dollars out of various urban markets and into vacation rental markets because they are being regulated out.Even the teeny tiny town that I’m from in Mississippi is working to regulate STR’s out. 

I've never spent a percentage in my life, so why would I use it to tell me if a deal is good or not? 

What percentage of a deal is fair for me to ask for when I bring a good cash flowing deal to the table?

Those are great questions to ask in terms of overall demand however they are subjective and based on opinion not fact or hard data.Follow up questions would be how many houses are on the market and how long have they been on the market, how many houses are under contract how long have they been on the market, how many houses have sold in the last six months and 12 months and how long were they on the market and what percentage of asking price did they close at?