how much of a down payment to live off of 35k annual

[Brad Pietrzak]

between me and my sweetheart we make enough to easily handle a multifamily property as a house hack even a single family home. but that is not what we want to do. what we want to do is put a large enough down payment on a duplex so that we can comftorably live off of her 35k annual salary and anything as I make as a engineer I can just invest for our future. we have only rented as of now. I am unfamiliar with the costs of homeownership. I have looked up some numbers and have a idea of how large of a down payment we would need to put. I wanted to get another opinion first. So duplexes in a c class area here run about 130 to 150k I could rent the one side as long as it is in good condition for around 8 to 900. I was thinking we should throw around 100k down that should give us a morgage taxes and insurance around 500 monthly enough to raise a family on her income alone all while not having to count on the rent so we can just treat it as a bonus and use it for more investing. Would you say that would be a large enough down payment? Or should I just buy it outright. I really am sorry if I sound stupid with this post. I just value multiple opinions before we move forward