I agree with Critter, it would be in your best interest to go to a tax professional.
Here are a few thoughts to explain the basics of how things work:
From your description, I would think Code 522292 (Real Estate Credit) would be applicable.
https://www.irs.gov/pub/irs-pdf/i1065.pdf#page=48
The Partnership (assuming that is the case) files a completely separate tax return. It reports the interest and fees as income. The amount of Principal Payments the Partnership receives is not reported as income (but it will show up on the Balance Sheet)
The profit from the Partnership is passed on the to the Parnters by K-1s. The Partners will pay tax on that profit.
The Distributions that the Partners receive are reported on the K-1. It is up to each Partner to maintain their "Basis" in the Partnership. If their Distributions exceed their Basis, that will be taxable. Otherwise, there is no tax on the Distributions.
If the loan is secured by the Real Estate, it is a mortgage and you may be required to issue a Form 1098 to the borrowers.
https://www.irs.gov/pub/irs-pdf/i1098.pdf
Again, I think going to a tax professional is in your best interest, at least until you get things established and figure out how things work.
