Financing new home purchase and renting out current home

[Kyle Ellrich]

I'm currently a home owner looking to buy a new house and rent out my existing home.  The issue is coming up with the down payment for the new home.  What ways have others financed the down payment for the new home?

Additionally, what concerns should I have renting out my current home with a mortgage, e.g. will the lender have a problem if I no longer use it as a principal residence?  Thank you!