900k on 290k income.

Me(28)and fiancé(27) are looking to buy a home in the Philly suburbs. I make 200k TC with stable job and expect income to rise to 250k in the next 2-5 years. fiancé currently makes 90k but will be a NP soon and will make maybe 120k. However we are planning on having kids soon and she will likely only work part time so may only make 60k a year. I have about 120k in stocks/cash and 200k in retirement accounts. and she has 250k in stocks/cash and 30k in retirement accounts. Planning on using 200k as down payment and keep the rest in stocks. Would buying a 900k house with 700k mortgage be reasonable. If that is reasonable how much more expensive can we afford and not be house poor.