Well problem is they put on a new roof on and day before closing its leaking.  

Here are the numbers: Asking price - $630,000 Down payment $126,000 Monthly Rent - $7,585 ($91,020 annualized)Expenses - $1,825 monthly ($21,891 annualized)NOI - $69,130 Annually10% Vacancy - $9,102Debt Service $3,000 monthly ($36,000 annualized)Cash Flow - $2,002 monthly ($24,027 annualized)Cash on Cash return - %19Cap Rate - 9.5% after vacancy deducted from NOIAverage rent $506 over all unitsThe property has new vinyl siding, new windows, and new roofs in the last 5 years.

Spreadsheets and websites are great for starting out but you will need to be able to look and say that roof needs replacing so for an 1800 sq. ft. house it’s in the 4 to 5K range.I can go on with other tidbits but that will get you started.

It is about 2 1/2 hours from Manchester, nh.We made it through inspection, it is a 100 year old house and needs a roof before the winter, I am figuring it should be about 15kish, but haven't gotten quotes.Putting 3.5% down with an FHA loan the p&i +mortgage insurance are $1200 a month taxes and insurance put it at about $1700, then $400 for maintenance/capex, and $100 for water/sewer and house electric, 8% $244 for vacancy.Current income is $3050/month, after calculating for maintenance, vacancy, capex I figure we should cash flow around $600/month.

I drove by the property, it's on a busy street, it has no garage, but the roof looks good and the siding looks good.What do I do? 

@Sundiata JacksonYou are going to need to save at least $1800 ($150/mont) a year just to deal with the eventual roof replacement, water heater repairs and furnace maintenance.  

A typical basic new build home is around $110/s.f and you are not building a roof or foundations, so you should be in range, depending on the specifics of your home.One question is if your existing heating and cooling systems are capable of handling the increase load, or if you need to do a dedicated unit in the attic for this room.

Does it need a new roof? 

At least with commercial (5+ units) you have shared roofs, can market a little easier (create a "wait list"), less exterior maintenance per unit, etc.

Purchased the house for $215,000 and invested about $25,000 for a new roof and other repairs and now it is valued at around $315,000.