The XIRR() fn works fine in the existing examples from the accompanying spreadsheet. 

Financing for 1-4 units is saturated, and there are hundreds of lenders in that market. 

They may focus more on the property’s income and your assets rather than your personal DTI.Negotiate with Existing Lenders: It’s always worth a shot to negotiate with the lenders who pre-approved you.

While Orlando is a huge STR market, I'm also aware that it is currently a tough and saturated market. 

I came from Florida and the market, while it’s hot (no pun intended), it can be over priced and over saturated!

Transfer of Leases and Tenant Information•Review the existing leases to ensure compliance with local laws and assess any terms that may need to be adjusted.

The only problem I now see is that I got sidetracked from my plan and now I'd like to pivot and adjust my routine to my interests and become the investor friendly agent, helping new and existing investors get their first or next investment.

That is probably cheaper to do and if the existing laundry are just hookups in a basement an upgrade that might give you a similar result in terms of tenant experience. 

If a renter wants to extend for a few months their stay beyond the initial lease term, will I be a) required to extend and b) at the same rate as their existing rate?

our yearly rent increases for existing tenants are usually $50/month or so (about a  4% annual increase)  … but this last year with all the inflation we raised them by closer to $100/month.