Every rental owner gets the form with box 1 filled in for rents. If he is asking you to put rental income in box 7 as if he worked for it, that is different.
A little more information would be good. He has at least 2 properties. He could be running the properties as a business. He could just have a few houses and your manage two of them.
I am unable to tell if he or his business is your client. I am including the directions for preparing the 1099-MISC (for tax years before 2020)/ NEC (for tax years 12020 and beyond). If he has a legitimate business, it may not even be required.
One solution might be who signed the paperwork for you to manage? Who hired you? Whoever hired you, him or Business X would be your client. Rent goes in box 1.
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