Line of credit on a cash purchase

Is there a certain time frame to apply for a line of credit on a home that you paid cash for?  I am trying to figure out a good strategy.  Ideally, I would want to buy a home cash, fix it up if needed and then open a line of credit to get my cash back and have the rents pay for the line like a mortgage.  Any info on or recommendations for this strategy please reply!!! Thanks!