This site is full wonderful hands on real estate I formation and also has well seasoned investors willing to share knowledge.

It doesn’t always have to be previous use of the site.

Hey Pete,Welcome to the site. 

I wouldn't just tape those up.....Hard to tell on pix, but it may just be dust that is accumulating in areas due to normal air circulation/turbulence....if that's the case, you really just need to clean the unit up...... dust will kill the efficiency of cooling unitsWorst case is that its something liquid leaking and its blowing that material across that surface and dirt is sticking to thatBy sealing it up without knowing the issue, you are just encasing the issue out of site and will likely just postpone needing to deal with it.Id take the covers off and take  a better look....my gut is that's it dust material

Assuming your not doing your own servicing then the majority of states you do not need to be licensed in but you need to register your company as a foreign entity.NMLS is probably the best site to research it but if you let people know what states your interested in then ask around.

@Brynn Hatch welcome to the site.

With that said, just wanted to say thanks to the BP site and members for all of the encouragement and support consistently displayed throughout the community.

They won't be amle to make their lot smaller than what is required for what they have on the site.

You will learn tons on this site and even more from the members.

I have seen on this website answers both ways regarding this (the site administrator saying leave it in Sch A, and his colleague (also a enrolled agent) advising that it can be written off in Sch E, but that there are certain restrictions mainly -- you must have passive activity gains where the deductions are covered (no passive activity loss carry over allowed.