Hi Jacob, congrats on making the decision to start your investing journey! I am both an investor and a realtor in the Des Moines, Iowa area. It looks like most of your questions have been answered by the other responses. I agree you'll need 20-25% saved for down payment and closing costs for your purchase. You don't "need" a property manager, but managing out of state would not be an easy task especially as a first-time investor. It's doable for sure, but I'd suggest having a PM initially. As far as you parents, I would put your financials together to walkthrough with your parents that detail out the purchase, mortgage, expenses, cash flow, appreciation, etc.
In terms of the Des Moines market, finding a multifamily in the $100-$150K would be extremely tough. Even if you could, you'd likely be looking at an older conversion property that will likely need consistent maintenance and wouldn't have the best appreciation. That being said, those properties can have great cash flow. If you have questions about this market in particular or want to see some examples what is currently out there and what the numbers would look like, feel free to reach out.