It really just depends on what you feel will be the return on your various options.
For instance, if you have cash, what are you going to do with that cash? Put it in short term treasuries and earn zero interest? Put it in the stock market and maybe make a killing or maybe lose half of it? Put it in gold and who knows how that’s gonna turn out?
Also, if you buy a quadplex now and the value of the quadplex drops, you might have a hard time getting your money out. Also, where and at what price you buy this quadplex will have a big impact on your return. Also, how interested are you in being a landlord?
Personally, I’m of the opinion that because the fed and the govt have made it painful to be a saver, most investors are taking on way more risk, while trying to chase returns, then they realize or admit. Consequently, very few investments are worth pursuing.
If you have cash, seems to me it’s better to use the cash to buy the house. If the house value drops, well at least you’ve got a place to live. It’s not the most daring plan, and you won’t get rich off it, but as mentioned, you’ll have a house to live in.
I’m sure that plenty will disagree with me though. There is certainly an argument that if you can borrow you should, as you open up the opportunity for leverage. (and bankruptcy too, but that’s a detail)