Rental Income and Taxes

[Miguel G.]

Can I use the income coming in from my rental properties to buy more properties? How is the tax going to be calculate it since I haven't paid taxes on my current rental income for the year? Supposed that after paying all expenses I have $10,000 in untaxed profit for the year. Can I use that as a downpayment for a new property? I'm just afraid I won't have money to pay my taxes next year if they tax me on $10,000.