I see mobile homes, and steel garages, and large steel girder buildings, but nothing that is something i can put together and finish myself, with floor joists like this one https://www.alibaba.com/produc... 

The website is mobile-friendly, so they've decided to stick with that rather than try to operate two different platforms. 

Currently, we have 4 mobile homes and land to add more.

However, I just found out Easy Self Storage started to sell their own access hardware, and then it released a new feature on their software/website that you can see gate access activities/log live and can even open/close the gate remotely simply through the website (even on your mobile!).

I have a deal in my hands of 7 mobile homes all on separate .25 acre lots and all rented out to long term tenants.

I personally won't be doing them here in MD, but some people specialize in acquiring those types of properties and I would strongly suggest you to attend local meet ups and try to speak with someone who had done it successfully and never got burned.

If you don't know better, it's easy to get burned. 

This would be similar to a Mobile Home Park, minus the mobile homes. 

Mobiles and land, fall into different categories.

I would rather invest my time and efforts in creating a quality life for me and my family , travel the world, enjoy the moment than burn myself out 7 days a week trying to build an empire of any kind.