My inlaws have taken interest in our real estate investing and would like to invest for both of our benefits. They're not from a country with a tax treaty with the U.S. So we either take the 30% flat tax or treat the investment(s) as a business. We plan to go the business route since after property taxes and expenses and the current market 30% takes a huge chunk out of the potential ROI.

Whether we purchase a single commercial multifamily unit or a couple of smaller multifamilies and short-term and/or mixed-use, can these all be under a single business entity such as a C-Corp or LLC? Is this even possible?

They will not participate in renovations or any property management (that's where we come in) but, they are looking to make a decent return on their money. Ultimately the business and the assets within it will be left to us down the road, so we will get paid to build and maintain it and have a ton of equity waiting in the (hopefully) distant future.

If you are someone familiar with this area I am very open to paying for a consultation to brainstorm potential structures and setups.