How much mortgage debt is too much debt?

[Stephanie Gledhill]

Is there a way to tell if you are taking on too much mortgage debt? I have a home that I live in that has equity. I am using a line of credit to start my real estate investment company. I am in contract on a home in Franklin, TN. In order to qualify for that mortgage, I have to put down 10 - 20%. I haven't decided if i want to pay the mortgage insurance on it and have more funds to buy another property. I will probably do 20%. Purchase price $500k expected rent $3200

I want to purchase another property in Idaho. I know I need to wait until property 1 has a renter with a year lease. I am purchasing B+ properties, buy and hold investor. 

I am using my Line of Credit as my reserves. Any advice about ratio's or numbers to look at when combining personal assets for your real estate investments?