I was thinking of utilizing an FHA loan to occupy the legal attic and rent out the first two floors.

That makes them whole, gives them a good lawn and keeps them accountable for their water and other utility usage.  

The reason is that you will likely pay a marginal more for property taxes after you renovate, marginal insurance premium increase, tiny bit more utilities, and that's about it.

How or where are you storing extra materials left over after a rehab.

Does the monthly rental fee generally include utilities, internet and cable or do the tenants pay for that independent of the rent?

For me, I see an increase of 25-30% on a $/sf basis when going past 2 units.It hope it goes without saying that building multifamily 2+ is always going to be more $/sf due to the separate utilities, extra kitchens, etc.

ARV = 235KAs is value = 225KRehab needed < 10K (mostly yardwork)Seller's motivation:Seller is 90 years oldFell ill over a year agoMoved into senior care facility, but kept utilities on thinking she'd eventually move back.

This is the further expanded category of Fixed Cost that I was referring to:Purchase Cost- Inspection Costs- Closing Costs- Lender FeesHolding Cost- Mortgage Payments- Property Taxes- Utilities- InsuranceSelling Cost- Commissions- Closing Cost- Home warranty- Termite Letter- MLS Fees

Last year (just after I was on the Money Podcast) I found myself with two vacant rentals where I was paying both mortgages and utilities, not only that but I had yet to refinance the one that was a BRRRR and I had used credit cards to pay the $25,000 in renovations.

I calculated roughly sending 800-900 per month after all expenses such as all utilities, PITI, repairs, etc.