It's called a home sale contingency. It may not be accepted by your seller but it is a viable option. It will require that you put your home on the market to sell within a specifiic time frame and within a defined price range. It was common 30 plus years ago not so popular today.
Talk to your agent about it.
Fran and Mark Redding
Prudential Fox Roach
1010 Stony Hill Road
Yardley PA 19067
You either sell at market value and take a loss on your current residence, OR you rent it out, converting it to a rental property, and buy another. You will have to document this and show on your tax returns that you are paying taxes on the income. I would speak with a lender to go over all your options based on your specific situation.
Typically to get a home now you will get one mortgage with a downpayment starting at 3.5% in the case of an FHA loan or 5% or more for a conventional loan. If you are a veteran, you can get a VA loan for zero down.
If this about having one home mortgaged and buying another you have to either sell the first one, rent it or pay it off.
You need a good agent and a good loan officer...that will make all the difference.