I guess I'm the yin to your yang: I don't think most people should jump in to REI unless they already have a robust stock portfolio providing substantial dividends and/or vast cash reserves so they can afford to dig themselves out when a sewage line clogs, a deranged tenant trashes a unit and has to be evicted, they miscalculate the ARV by more than their profit margin because they forgot to double their back of the napkin rehab budget, tariffs cause the price of lumber to double during permitting, or something expensive and unexpected inevitably goes wrong.

It states in the current lease that the property is to be kept in a sanitary condition at all times and I can't really thing of anything more unsanitary.  

For sanitary reasons, I want those floors sealed and under three good coats of extremely durable oil-based semi-gloss polyurethane.

Please feel free to PM me and I'll give you some quick insight as to a high-level approach (as in the 30,000 foot view) to what you realistically need to do to determine if it's feasible and how to do some financial forecasting on the "back of a napkin" to see if it makes sense to move forward.Good luck!

The reason why I'm asking for an estimated percentage is because I'd like to do a quick back of the napkin calculation before I get the T12 from the owner. 

One of the general requirements for selling a house in much of my county is that a dye test has to be done on the drains to see if they're working properly or if the water off your roof is going into the sanitary sewer system, which is a no-no.

The issue is that the property is not clean and sanitary in accordance with the lease agreement.

You may want to consider portable units (e.g. shipping containers) for Self Storage for a few reasons or as you mentioned RV, camper, or boat Storage but WITHOUT any building (no garages, 3-sided stalls, etc.) just dirt & a fence for security and get some immediate cash flow coming in.Yes, you're going to need to do some "back of the napkin calculations" to determine your costs and potential revenue for whatever specific route you go, but you're also going to want to do a market study & check out the competition to put into context as you can't evaluate in a vacuum.For instance (and this is a basic example just for expediting my point) if you want to build an RV/Boat Storage and when you look around the only other two in town are hardly used, then not so good. 

Clean, sanitary and safe.......If they want to talk about paying more in rent, then we can talk about making it a nicer unit.

there is no written word that states you have to use a professional program.. you can literally hand draw on a napkin but if city is requiring architectural sign off and inspections for some reason then you are better off just hiring out.. youre looking at 750-1500$