Any advice, tips, or input otherwise would be greatly appreciated. 

Good luck, now the question is are they impressed by the quality of the calculator or that they actually have a serious investor willing to do calculations at all :)

Ask contractors, most investors will have a trusted contractor that they will hold onto for dear life because they do quality and affordable work, you will need to find that person who has experience building multifamily properties. 

Long term commercial debt lenders make adjustments but does not generally follow that.For high quality assets i am currently seeing about 4.8 percent for 10 year debt. 5 year fixed I am seeing about 4.5%.If a life insurance company they can go lower on rates but want minimum 35% down and more picky on the properties to lend on.Seller financing can be great BUT just remember to not way overpay for an asset just to get that.

The one tenant mentioned there are gaps for air flow, which they tried to correct on their own (prior to us owning). 

It probably depends largely on the type and quality of the subfloor.

If anyone has any tips on how to get started or any insight into doing business in the LA market please let me know.

The quality of neighborhood starts deteriorating...

Pros:Strong cash flowMajor affordable housing shortage in the countryBarrier to entry - zoning prohibits new parksPride of ownership - the residents own the homeLower operating costs - the residents own the homeLower touch - the residents own the homeSticky residents - costly to move a homeEasy to raise rents - costly to move a homeRecession resistant asset class - affordable rentLarge private equity funds are entering the space - drive prices upMom & pop ownership - opportunities to improve NOI and valueLower entry cost per door - less capital neededCons:Not sexy - smaller resale pool (but that's changing)Stigma - some counties try to stop operations (poorly operated parks, criminal activity)Stigma - some people don't want to live in oneLower credit quality residentLess appreciation potential, unless forcedNiche investment - helps to have scale to properly operateMany banks don't understand it - tougher to financeOlder assets in many cases

I'm looking for a basic cleaning service for a short term rental (air bnb) in Jacksonville, FL.