I only include known numbers...in this case principal, interest rate and PMI as stated by Robert.  

"if I only knew then, what I know now...."

I only have about 10k in savings and was wondering if I should wait 3-4 months to purchase a 40k SFR cash or should I try to seek out private/hard money?

Maybe someone can tell me of the negatives of my thought process but I personally would rather my tenants make themselves a few extra keys to have as spares or give to a someone they trust just in case they need.

Here is a link to the original video I did:http://youtu.be/QSBJCdkAhgIThis is a REO in Southern CA in a typical neighborhood, house had several negative features (backs up to main street with traffic noise, shared lot line, small lot).

If your rent for $2300/mo, you are going to run negative as that doesn't account for ANY repairs, maintenance or vacancies.  

As a CPA, I make complex things simple and simple things complex.I have a formula of Square footage x avg SF rents (Avg sf rents is from phone calling Sunday ads)(Since I only buy close to downtown (e.g. yuppies) I add $100 on top of this)Less PITI -Principal, interest on 10-20% down on 15yr mortgage -Taxes, insuranceLess depreciation=tax income+ depr (add back) - principal payment (deduct)=cash flowMy "business model" is net $200-300 per house (yours can be different)Agree w prior posting that debt service is arbitrary re 15 yr vs 20 vs 30 yr; % down; etc.I have a very successful friend who never pays 60x rent.

As for zillow use, I only used zillow to get an estimation of value.

Apparently they can afford a negative cash flow, or they aren't on BiggerPockets and don't realize there's going to be a negative cash flow.

If you have to borrow in order to buy in your IRA, the borrowed money will be subject to taxes that negate the value of the IRA - This puts you right back at point one.