Hi @Tim Robbie, Nick gave some great advice but I will add on.
To answer your most recent question, to maximize the methodology, you would buy the first 10 properties using conventional financing where you get the best rates and terms.
Then, you can get other types of financing. You can purchase properties with non-QM loans that are not agency loans and do not come with the same restrictions. Essentially anything outside of FHA, USDA, VA, and conventional loans are considered non-QM.
Non-QM loans come in all shapes and sizes but the most common one for investors is known as a DSCR loan.
This is a loan where there is no income or job verification, you qualify based on the income generated by the property. You do not need to submit a laundry list of documents and the rates are not that much higher than conventional so many investors choose this option for scaling.
You could also refinance all 10 of the properties into a non-recourse blanket loan where there is one loan to cover all 10 properties. This frees you up to do conventional on your next 10.
You could also mix and match these strategies. Maybe it makes more sense for you to do a blanket loan at 15 units so you do 10 conventional and 5 DSCR.
Small multifamily, large multifamily, and single-family all work, and all can generate the income that you desire. You need to make sure that you have the right team in place that can make it happen for you.
Hope this helps! Let me know if I can be of any assistance.