"...The Church has maintained certain real estate holdings, particularly those contiguous to Temple Square, to help preserve the beauty and the integrity of the core of the city. All of these commercial properties are tax-paying entities.
"I repeat, the combined income from all of these business interests is relatively small and would not keep the work going for longer than a very brief period.
"I should like to add, parenthetically for your information, that the living allowances given the General Authorities, which are very modest in comparison with executive compensation in industry and the professions, come from this business income and not from the tithing of the people."
https://www.lds.org/general-conference/1985/10/questions-and-answers?lang=eng
If these allowances include travel, lodging, etc... for all eight quorums of the Seventy (as well as living expenses for the First and Second quorums, the Twelve, and the 1st Presidency), then I'm not sure how much money would be left over for sports.
But maybe the bigger question is if a lack of money is BYU football's largest obstacle - or even much of an obstacle. I've always assumed that our greater obstacles were 1) the difficulty of recruiting to BYU's academic and behavioral environment, and 2) the soft limit on paying coaches excessive amounts because professors would complain about the perceived unfairness.