Aside from the real estate websites (idealista, sapo,Imovirtual) and AirDNA, is there another website/source that we can use to analyze the areas?

is there a tool on this site? 

(https://www.mynd.co)One of my co-workers at my last job (pre-covid times) used to work\invest with them, so I had probably registered on their site back then.

For the community development dept, you'll need proper plans (architect), site survey, permits, etc. when you're ready. 

Is your income considered variable in nature depending on job sites and that you do not work a set amount of hours per week?

We take ID's for all guests (in a website called Chekin) so would have documentation the booking guest is above 21.

I found what seemed to be a great property with a house for an STR and other space that I could expand for camping/RV sites and a barn that could be converted into a venue for events. 

I really would like an app or site that allows you to compile a list of properties with notes on the spot, and bonus points if it pulls up any info on the property as well. 

For example, if I purchase a site entitled to 100 dwelling units under a newly formed holding company and the only thing linking me to it is a shared PO box mailing address on the holding entity, the lender gets alerted.

You can hire a few different virtual assistants on a website such as Upwork.com, train them on how to skip trace, and stick with the one that is the best.