Sorry to bust your bubble but you cannot buy another home with very little downpayment anymore. The lenders have really tighten their standards.
Read this article...it will also provide the link to the government website.
FHA limits 'buy and bail' purchases | Real Estate and Technology News for Agents, Brokers and Investors | Inman News
Too many people in the early part of the year were doing "buy and bail" methods where they purchase a new home while telling the banks they are going to rent out their old home. However, these people have every intention of defaulting on their original loan (maybe they were underwater and had no chance for recovery). So these homeowner produced rental lease agreements showing that they would have enough income to cover their old mortgage and they would still have income left to afford their new mortgages.
Once they closed on their new home, they just stopped paying the mortgage on their old home. They don't care if their credit is ruin because they had already locked into a mortgage on their newer cheaper house at a good rate and have gotten out of trouble with their previous home that was losing value (or probably underwater).
If you want two mortgages, you need to show the bank the you can afford 2 mortgages alone without any rental income counted. (this is unless you can show you have at least 30% equity in your old home).
I believe you still need to put 20% downpayment on the second homes with most banks now anyways. Maybe they will let you have a 10% downpayment on a second home if you can show them you have an average of 6 months of mortgage payments in reserve in your checking/savings account. You will need to show them your checking/savings/investment account from at least the last 6 months that shows you have had this money (there are red flags if they only see you have this money come out of the blue recently) It usually has to be an average balance.