The house itself would not cause him probables with disability payments. However, the rental income and management activities could cause two separate problems.
First, the management of the rental units could be considered by Social Security as "work" that would show that he does not qualify for disability because he is capable of "working." (I.E. acting as a property manager.)
Second, even if he does still qualify as disabled, if he does not have sufficient work history then his disability will entitle him to low income benefits (SSI) instead of typical SSD benefits. The low income benefits are based on both his disability determination and on his income and assets. Since the property is his home it will not count as an asset that must be below $2,000. However, the income will reduce his SSI benefit dollar for dollar based on the rental income.
With all that said, it is very likely that this property purchase will cause him problems with any benefit that he may be entitled.
I cannot provide you with legal advise. I have provided you with information about the law related to your question. My answer, and any information that you find online, should not take the place of having a consultation with a lawyer in your area to advise you regarding your specific issues.
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