I’m in Ontario, Canada, so a lot of the US regulations don’t apply. 

Once you know the houses in your area pretty well, using those 25 components makes it a lot easier to estimate back-of-the-napkin.For example, I know that for a specific type of four bedroom, two bath house in my area, it costs about $2,000 for all new electrical fixtures, about $2,000 for all new plumbing fixtures, about $3,000 for interior paint, about $7,000 for new flooring, about $8,000 for new cabinets and countertops, about $2,500 for all new appliances and about $1,000 for miscellaneous cosmetic stuff.So, when I walk into one of those houses, I know right off the bat that I will spend about $25,000 for a full cosmetic rehab.But that exact same scope of work for a different type of house with different finishes in another state where I rehab would cost much different for a cosmetic rehab. 

The project is almost halfway done...but may need some minor improvement to the existing condition.Basically, the framing, electric, HVAC extensions, and plumbing are mostly done.

This means I know my way around a lot of the basics of many trades including plumbing, electrical, carpentry and of course HVAC.

The goal would be to have it written in the contract that I’m allowed to list the house or unit on Airbnb in a neighborhood that doesn’t have regulations against.

When you inspect the rest of the house, you should get a feeling as to whether there are likely intentional plumbing issues or not.

Do you know the liqour license requirements where you are, do you know the other regulations you'll need to follow. 

My advice is to know your market - KNOW THE LOCAL REGULATIONS, know what kind of demand there is, a realistic sense of occupancy and revenue, and a realistic sense of your expenses.  

Vinson's Plumbing is super reliable.

Is this a California regulation or  Texas?