I’m with SD R. I dislike guaranteed loss due to PMI and higher interest more than potential loss due to money not being in your 401k.

Since you are a first-time buyer you should be able to withdraw $10K from your IRA with no penalty. Your can always tap into your Roth IRA if the things get real bad. Also, some of your monthly payment will go towards the principal and the difference in cost between buying and renting less dramatic. And you can think of the principal as a form of contribution to your retirement fund – the house today is more tangible than 401k distribution 25-30 years from today.