as alluded to above, retirement accounts count as reserves in the eyes of the bank, so thats all good. You would want to be able to cover a major expense without using that ideally but you can in a pinch.
Don't overlook dollars to pick up pennies; a mutually beneficial seller finance deal for a good property is an amazing opportunity and I would put my energy into that first. A lawyer drafted promissory note and clear terms is a necessity. Make sure terms of exits and refinances are clearly outlined. This interest rate environment offers a great chance for your in-laws to have a safe ongoing return and you either a lower downpayment entry or excellent debt structure. And having the cash on hand to light rehab is a great way to gain experience
As for the "zillion" properties...there is some safety in numbers as you will have income likely have income coming in even as you wrestle with the expenses in one area. Just make sure you underwrite using appropriate projections of vacancy, repair and capital expenses. In any given month(s) you will likely be ahead in one or more or all of those categories. Thats cool, but remember they are reserves.
Seems like you are in better shape than you think you are.