sister and brother in law visit visa

Hi ,
My sister and brother in law are applying for UK visit visa to come and visit me for few weeks however my brother in law is a property investor and only receives commission that is deposited in his personal bank account. Now there is no other document to show proof of income other than personal bank statement as self employed investor. he is also submitting his property ownership documents that he personally owns and resides in. I cant think of anything else as proof of income from self employment. will it all be enough

can someone please answer my query on urgent basis