I would suggest to have an agent represent you but only if it is a very good friend of yours or if your related to the agent!

I would recommend getting more established investing before doing partnerships with your relatives money. 

If a family member puts a lien on the house using his self-directed IRA, depending on your relation to the family member, it might be an outright prohibited transaction for you to pay interest, or for them to sell you the property.

Back to your question, my advice is to not "ask for money" but offer your relative an investment option pointing out the benefits.

Could be a tax issue for your relative since the IRS could consider it a gift and you might have to pick up the interest as income.

No need to spill the beans if it's a secret investment strategy or if your relatives are still in the dark.

Your relatives can get one and in turn loan you the funds and charge interest which you can deduct.

But all interest income on the loan to your relative's IRA will be tax free.

If you haven’t had the conversation with your relative about getting those “unofficial” tenants out, I believe you should do that soon and present your plan how it will be beneficial for both of you and you can begin the process of getting new tenants in. 

What is your relation to the company?