With GEICOs online portal I can go in and add/subtract properties as they come/go in my rental portfolio.

I have a few clients that I'm helping out and maybe some Houston area flippers can help out a little.They're all looking in the 60k-120k range and I'm finding flips with around 16-21% returns (I'm subtracting 10% of the ARV for commissions, insurance, utilities, escrow, taxes, etc.). 

I would assume $100-200/month capex (depending on age of house), 10% of rent for management (assuming you don't do that yourself), and 2-5% vacancy rate depending on market (subtracted from your monthly cash flow).

It's correct that you subtract debt service, but you have to remember to add back the principal paydown at the sale. 

I then multiply by .7 and then subtract the repair estimate cost of $10-20 a sqft.

every time you put a "deposit in the jar" subtract from 1000and put the new number like , deposit 125 dollars and cross off 1000 and write "875"Then do it again.Shoot for $5000.

Figure out what the principal, interest, insurance, maintenance, taxes, etc. would be on that property (worse case), subtract out what you pay for rent, and try to save at least that every month ... this will not only help build your personal finance skills, but will also simulate what your finances would look like after you purchase the property ... if you are late or short even 1 day or dollar or don't like how your life is during that simulation, then you won't like it after your purchase ... you'll need to lower the simulated expenses until you are happy with it ... from that you will know how expensive a property you personally can comfortably afford and save up a down payment for it.

Otherwise you will calculate the Square footage and subtract the SF you are using/living in.

Figure out the ARV subtract the renovation costs subtract the flippers profits subtract your desired fee. 

.- Invest the money and hope for a positive ROI.The math looks like this for the student loan payoff: $281.69 * 10 years * 12 month/year = $33,802.80 subtract out the principle of $25k and a savings of $8,802.80 is left.