I got a call from them today seemed strange upfront fee with no listing agreement I called some bank contacts to see if Core is real.  

He is now in a lease option agreement with the original sellers and is stating I will get my assignment fee when the property is finished rehabbed and sold (likely months away). 

My question is, why would you withhold any information from the person you now have to sign an agreement with to help you find a property?

However, consider:Long-term market projectionsYour personal financial goalsTax implications of holding vs. selling (consult a local tax advisor)Partnership Structure:Clear, written agreement detailing responsibilities, profit sharing, dispute resolutionRegular financial reporting and meetingsExit strategy for both partiesConsider forming a legal entity for the partnershipFull Bank Financing: If the bank would finance the entire project including renovations, this could potentially be more advantageous.

Also in terms of collecting rent, would I need a lease agreement, and account for this during tax season.

Hard to tell from here, but your prices seem very high, although I do understand that "emergency" service during the high heat season will cost dearly...As LL, appliances, including HVAC that you have provided in working order, you need to repair or replace as needed unless local law AND your Rental Agreement state otherwise, obvious misuse/abuse excepted.

We also have a written agreement stating that the ORIGINAL Borrowers have relinquished any rights they may have to the escrow impound funds that exist or may exist in the Escrow Impound Account.

It also is helpful to have a California LLC in case you ever sell that property and move into another state so that you do not need to form a new LLC altogether with new operating agreement, just re-register in the new state as a new foreign LLC.

I’ve heard attorneys who specialize in self directed retirement accounts say you can put the lease agreement together and even show the property to prospective tenants andof course you could manage it.  

Creative Financing StructuresThere’s also the possibility of lease-option or lease-purchase agreements, which allow you to control a property now and buy later, often with part of the rent going toward the down payment.