You need to post it and notify all tenants of the updated policy and the amount of the fines.

Any profit you can make from STR will help with the mortgage, but it's a bad idea to count on the STR to make a certain amount of money if that's the only way you can afford the house. 

A rider allowing for using your owner-occupied property as a short-term rental for a specific/limited amount of time is very different than an investment property being used as a short or long term rental 100% of the time.Also, telling your home insurance company that you STR your home occasionally does not give you extra coverage for those types of risks, it simply means if your renter burns your home down the insurance company isn't going to immediately deny your claim. 

It may take decades for the land banking strategy to produce results (if it produces results at all).In the same way that any investing strategy comes with its fair share of risk and uncertainty, these issues are compounded by the amount of time required for the land banking strategy to work.

The credit cards can be stifling, but in the grand scheme of things, $40K isn't a ridiculous amount.

Competition with owner-occupants and the age of the homes (70-120+) will squeeze your margins and expose you to a fair amount of risk.

I'd like to get $30k, I'm just not sure how to calculate the percentage of ownership that would amount to.

My experience is that the major platforms want two things1- sponsors with a verifiable track record of success in the same property type2- sponsors capital investment in the projectSponsors utilizing these platforms have a large "gap" to make up - that being the difference between the amount of capital raised and how much of that capital goes into the actual asset, vs how much goes to fees, costs, etc. 

Assuming I also use the Airstream for lodging while traveling for personal reasons, would I just take a pro-rated amount of depreciation for the amount of use that is business vs. personal?

I am on the other side of the bridge in Virginia - there is a good amount of DC area people here on BP