The "50% rule", that says all expenses, capital improvements and vacancy will eat up 50% of your gross scheduled rent.

I historically have required a tenant's gross income to be at least 3 times the monthly rent, but I'd like to know if there is any sort of industry standard.

Being a partner in a mini-storage I can say with confidence that your expenses will be higher than $7-8K if gross scheduled revenues are $25-27K.

They incurred additional costs along the way that cut into that gross profit.

The one that I was watching had a three unit building that grossed $4,000 per month.

I don't see how that is possible. in two years you would have recieved gross rents totaling just over half your investment:600$/month X 12months X 2years = $14,400.Now subtract your property taxes and insurance and expenses (inclouding time spent).

Gross rent on the four is $2900/month.I have private money lender in place who will give me loan for full purchase price at 5% interest only with a 5 year balloon.

Fastest growing metro economy and projected to keep up the pace for years to come.Austin leads the nation in gross metro product, and is predicted to keep the number one spot through 2020.  

Not factoring utilities my gross rental income is $1350 per month, PITI is $866, a net of $484 monthly.My salary is $3000 a monthI also have approx $500 of side business profit per month (probably won't apply to my debt to income ratio).I also have about $280 a month of student loans.So, my question is, how can I use my rental income to let the bank give me a loan for a second house?

They've done probably a dozen jobs in my neighborhood since then, which I'm guessing added about $100K to their gross income in the past year; the ad cost me $400, and my painters will reap the benefits for a long time to come.