I have known people who get creative in having others cover their mortgage payments. I personally never had the opportunity or the courage to try what they did on my own.
The first person bought his parents’ home from them in his freshman year of college. He then rented out every room in the house that he could. He kept the master bedroom for himself but rented out the other two. He rented out the family room and spaces in the basement. All to fellow college students.
My understanding that this was also all done in cash, so he never had any declarable income. He was also collecting more money in rent than his parents were charging in mortgage, so he lived for free and paid off his mortgage shortly after graduating college. He finally kicked out all of the tenants when he got engaged.
The second case the guy rented out his garage to a landscaper who needed the space for their trucks and equipment, he and his wife parked on the street, they were in Chicago with a end unit so parking was ample.
They also had an apartment that they set up in the basement and rented out, with only a microwave and hot plate for a kitchen.
This one didn’t get his mortgage fully covered, but he did get cash and free lawn service.
While the cash aspect and tax avoidance is not certain. I do know that these people had others covering up their mortgage or a nice percentage. It can be done, legally and I am a bit jealous of what they saved.