My only problem has been a commercial space where a hair salon had to shut down due to covid and I let them out of the lease. 

For instance, what if you had a fee that said that people with brown hair had to pay an extra fee. 

@Randy D for revenue industry standard is charging a flat fee (see chart below) or a consistent percentage of the monthly rent(8-10%). 

In terms of legitimate numbers, besides the construction cost above, remember that the majority of these homes are very old and adding rooms can be tedious, stressful, and might make you want to pull your hair out!

Also, be sure to have multiple car dash cams, and ring cameras in every room.Don't ever go in the same room alone, never close the front door or any door in the house, never look her in eye, for goodness sake never make any comments about her clothers, hair, appearance......depending on what specific things listed above, you think are a joke or good common sense, will determine your level of neuroticism about the topic and should probably let you know if you have right mind set for the leasing agent job...jus sayin

I know its splitting hairs and probably wont matter, so I'm just wondering.Thank youJohn

Central heat & air*I made this below chart based on this community shared knowledge (Thank you all). 

Central heat & air*I made this below chart based on this community shared knowledge (Thank you all).Need1. would you consider this property at all ?

Currently the first floor is a hair salon and the second floor is a one bedroom apartment.

Look at this chart.