I’m always looking to implement best management practices so what can I, as a landlord, do to protect myself when accepting online payments?

The PM group I'm using do great work, per reviews.

@Yosef Ajami, we use Quickbooks Online for all of our Clients (including syndicators).

Shoot me a text or DM and I can give my $0.02 on it after reviewing the deal - thanks and good luck to you! 

Are there any references or reviews you can check?

Mount Airy in particular is probably the most difficult neighborhood in Philadelphia to learn and there's no way you can do so from a computer reviewing rental rates and crime assessments. 

We are hoping to avoid doing any sort of partnership and maintain a single member LLC, but searching online hasn't been fruitful.

Find ways to consistently and systematically add more people to your database each week - i.e. cold calling, networking, online marketing4.

Then just yesterday, I come across the 1099 / 1099-NEC form requirements online from my own research.

You'll need good contact info for them to be able to collect, and ideally the new address for the tenant however which if you don't have can probably be found easily with some online sleuthing/ contacting their employer, skip tracing software, etc.