I plan on buying a condo/townhouse in the near future on my current income. In ~3-5yrs I will probably need to move into a larger place as my family grows. I would like keep the first property and have enough saved up for a down payment on a second by that time. I would then rent out the first property. What are some things to do in order to ensure I can afford the second mortgage? I expect my income to have increased by then. My wife may very well not be working at that point. She does work now, but her income is considerably less than mine.