The rules state you cannot extend credit to your IRA, and your IRA cannot be used as security. This makes borrowing money a little more difficult, however, it can be done.
As long as you get a loan that doesn’t take recourse against you or your IRA, you aren’t making a prohibited transaction. What most individuals do is use a property owned by the IRA LLC as collateral, as long as the loan-to-value ratio meets the right requirements, most banks will loan money to the IRA LLC.
Gains off of debt financing may be subject to Unrelated Business Income Tax (UBIT) and you would most likely want to hire a tax professional to assist in filing a return.