We vastly prefer brick-veneer properties when we can get them, slate roofs always a plus, the least major upgrading and modification on the original build possible.

I contemplating upgrading to a natural gas.

You should be able to get into a property of up to 4 units for little to nothing down and you can use any saved funds for repairs and upgrades. 

Sure, you can create one, but just be conscious of whether it's for a business need or risk mitigation. 

Needed upgrade to bring it to current market value.

Are there any upgrades I could do, that I’d enjoy while living here, that would help if rent for more to justify making the upgrades?

There are gas lines in the street, but obviously the cost of upgrading the home to gas is considerable (albeit probably less than installing solar.)

If we get a trailer, small house, or condo, the plan would be to initially live there and continue to build assets until either moving or upgrading, then renting out the previous one. 

After reading the bigger pockets books and learning that I should be putting money away for vacancies, upgrades, repairs, etc...should I have separate bank accounts for security deposits, vacancies, and maintenance?

Agreeing with most here--definitely a great deal for you compared to continuing to rent, plus an upgrade on your housing.