Am I doing this right, can somebody check my math and logic please?

That's a new furnace every 6 weeks.My point was your math (3% of purchase price every year) is offIt should be about 8-10% of yearly rent (In your case around $1400, for the year, not monthly)This expense column is for leaking sinks and such, 12k is far too conservative for a double.

You follow that simple math, and you will do pretty well.

The math may be a little different if you are buying leads as an agent vs. as an investor.

I tried attaching the document I used to do the math, but can't seem to know how to do it correctly.

Owner occupied attached single family dwellings are in the same loan programs as single family, the down payment for 4 will be 25%, it's been a very long time since I've seen 5% down on a duplex, 10% I'd guess would be the minimum any mortgage banker would take on, mortgage banker meaning wholesale secondary market.

You almost have to get the land for nothing so if the premium tenant doesn't happen you can make profit from the secondary tenants if you have to buy it and wait or get cheap extensions.The costs for those projects can get very expensive.  

As Bill Gulley has mentioned, HUD uses 30% of income for the contribution from their Section 8 tenants; that is pretty close to 3x so we use 3x to keep the math simpler.

My math was, I buy for $99,500, it is worth $102,300.

Be careful if he just deeds it over to you because any secondary liens transfer.