This will be considered self-dealing and is prohibited by IRS regulations. You cannot use a SDIRA to invest in something you will self-manage. You have to invest in something that is considered "out of your control" for the retirement protection it provides against your own misfortune. People may do things that are against the law, but it doesn't make it legal. Why risk your retirement savings on a stunt? If you want the tax savings of the IRA investment, you are supposed to put the money out of your own control. That's what the custodian is supposed to be supervising on your behalf.
UDFI or UBTI is a concern also, if you leverage a tax exempt investment there are special rules that tax your leveraged profit. This is regardless of who manages the investment, I.e. even if you do it right investing through a fund.