As a bonus, you can use it for your personal record keeping as well.

My property manager is insisting he only needs one person to sign it given he only needs one SSN on the W9 for tax reporting purposes.

But yes, you should have a CPA, and the one smart enough to properly prepare your taxes over the years should have an easy handle on this too.

Where to start with guidance and then drilling down what my personal potential is?

Send him a letter, emphasize that you are personally yourself the end-buyer, include proof of funds, include something attesting to you being financeable (unless your proof of funds is for the full cash purchase price).If he owns 20 local businesses, good chance he's in at least one chamber of commerce, and if he's not, he 100% knows people that are, who will spill the beans and offer to do an intro if you mention you're interested in buying a gas station over a beer or a meal (there's probably like 3 people in that city that fit this description, why not get introduced to all 3?)

I would like a software solution that handles both. 

I can send you a couple blogs that provide a comprehensive overview and I'd also recommend you check out Doorvest - they essentially handle the BRRRR strategy on your behalf.

Also, while I've read some horror stories about assessed value increases, our personal portfolio came out relatively unscathed during this recent batch of tax bills.

If you feel the leasing services are being handled poorly, perhaps you should also take a closer look at the day to day management.  

I plan to hand write the letter to keep it personable and local.