I have 140k gross income last year, no other debts, first time home buyer.

After 10, then 20, then 30, I held a gross number for all like $12k up to 30.  

I have a prospective tenant that filled out an application.However I need some advice on qualifying this individual.The current rent is 3600The applicant is a family The Spouse doesnt work The main applicant gross W2 income is around $10000 monthThe monthly net income is $5700No car loan's No credit cards balancesThey pay $800 month on a personal loan.Since a rent check is written after net income is received.

That seems a gross oversimplification that can result in bad returns.I've personally invested in some low cost markets that gave me great cash flow and above average appreciation. 

As a rough approximation, you can expect E TN gross annual rental revenue to be around 15-20% of purchase price at most price points & home sizes.

Don't stop until you hit your target gross income goal (think retirement and replace your 9-5 job). 

8- 10 % net or gross? 

For instance, what is your note worth, what is the house worth, monthly expenses including mortgage, and gross rents, ect.  

California charges a minimum tax of $800 a year per LLC, and more if you have gross receipts in excess of $250k.

The leases that I've been involved with for the feds are very specific as to what they will and won't pay, what is needed in the space,; and, most of the leases are gross leases wherein the Landlord has to calculate many unknowns.