Couldn't I list it myself somehow, paying a small fee, or even simply sale as a FSBO, utilizing a 2000 marketing budget or what not?

It also means you are paying an extra fee for this middle man structure.  

(Mgmt Fee = CapEx % since this calc does not have that)

Then the investor assigns the agreement to a tenant buyer with the approval of the seller and the tenant buyer assumes the rights and obligations in the lease option agreement and the investor collects the assignment fee and moves on.How would a real estate agent assist the investor in this process?

Property taxes, insurance, utilities, HOA fees and loan/financing costs are some of the ones I've recently learned about.

Our strategy is a 3-5 year flip that when you add up the cash flow, the tax savings from depreciation, the mortgage debt pay down, and the fact that we bought it under market value and that we are selling it on a lease option so we don't need to pay realtor fees and have minimal closing costs, our average total profit over a 3-5 year period is round 60k per property that my partner and I split.  

There's a lot of red flags on this and I would personally move on.If you still want to pursue it after looking at their background and credit report, might I suggest  a higher security deposit or pet fee up front.Still, there's always better tenants out there for you.

Curious what everyone charges for deposit, misc fees. late fees etc. $900 month rent. 

Obviously, you should consult with your CPA and lawyer (trust me, pay the fee, it's worth it).

I guarantee when that person gets their first referral fee they'll search even harder for you next time.