So, if your Self Directed IRA is 75% partner with another entity, then it must collect 75% of the profit (rental income, sold gains, etc), it must also contribute 75% of the expenses (rehab, insurance, taxes, etc).I am not sure about loaning to a partner. 

You will spend around half of your rental income on the maintenance, taxes and operating expenses of the property.

What would be the best percentage to use when analyzing income,expense,prop value increase? 

He told me that we can't do that and that it is a partnership.In looking at the IRS definitions it states:PartnershipA partnership is the relationship between two or more persons who join to carry on a trade or business, with each person contributing money, property, labor, or skill and each expecting to share in the profits and losses of the business whether or not a formal partnership agreement is made.The term "partnership" includes a limited partnership, syndicate, group, pool, joint venture, or other unincorporated organization, through or by which any business, financial operation, or venture is carried on, that is not, within the meaning of the regulations under section 7701, a corporation, trust, estate, or sole proprietorship.A joint undertaking merely to share expenses is not a partnership.

If it is saving you 5% on your mortgage interest you are at a negative income of $737/month before any expenses on the property.

How much do you expect to go towards expenses of an old home?

We're in our 70s now and our biggest expenses are for a new Lexus every couple of years and first class air fare.

According to my numbers, and given the sellers rough expenses...

Just looking at your numbers, I don't see any monthly expenses for vacancy, Capital Expenditures (you may have this wrapped up in repairs), or property management.

Or maybe they're buying a wholesale deal off-market, and banks don't like the fact that an assignment fee is involved.Hard money is more expensive, but usually gets the job done quickly.