I do everything from day one when it comes to turning their gross outdated foreclosures into practically brand new homes.

A 7 unit property plus a single family home with over 4K gross monthly rent for 160k.

Purchase price: $569,000 Cash invested: $80,000 Short term rental cabin in the Smokey Mountains generating in excess of $90k/year in gross income.

We have income from our 4 unit multi family that grosses $5,000 monthly and after regular expenses and maintenance and paying our mortgage, we cash flow $500 per month.

So with our ranges stated here your developer is looking at $850k-$1.6M gross profit.

Also, while not an expense each month, you should include about 5% of the gross rent as capital expense reserves, so when big ticket items like the HVAC or roof need replacing you have funds to do it and do not go further into debt. 

Gross Rent Income: $1,743Property Taxes: $277/monthLandlord’s Insurance: $238/monthRepairs & Maintenance: 10%Vacancy: 8%Capital Expenditures: 10%Property Management Fees: 10%Electricity: $0 (tenant to pay)Gas: $0 (tenant to pay)Water & Sewer: $0 (tenant to pay)HOA: $33Garbage: $10/monthLawn Care: $100/monthPest Control: $50/monthSnow Removal: $50/month

I understand each of these are slightly different (a PM is a monthly expense whereas a vacancy may only happen once in a blue moon), but to conservatively analyze a property, it seems like the safe bet is to subtract 35% of the gross rental income to save for the reserve costs.However, it seems most people analyze their deals ignoring the expenses that are not from PITI, which makes understanding how something "cash flows" puzzling. 

What did your gross rents come out being monthly?

That depends in part upon your debt to income ratio, if you plan on living in the property, and how many units the property is. this is the ratio of your gross monthly income to your monthly obligations (credit card payments, student loans, auto payments, etc.)