We built a small recreational cabin and then rented the additional land to a local grower who added improvements to the land since the rent was so cheap.

We added value by improving the land and building a small recreational cabin.

Once you move into commercial, improving a property's profitability has a direct impact on it's value.

But there are a few caveats: 1) we technically have no primary residence since we live overseas on US government orders (and our housing is covered), 2) we own 3 investment properties and we were told we could not purchase any more properties (could not exceed 3) while we had the HELOC open (we were using the HELOC to cover improvements), and 3) this was a year ago, when the economy was good.

You mention doing your own maintenance and Repairs and capital improvements (roof, windows, furnace, water heater, etc). 

I'm not sure if I'm understanding you correctly, but basically the LTC you can expect will come from your background: credit, experience, etc.If you want to improve what you can get you can bring on a partner who adds to that background so you can be more fundable as a team.

I just heard from my employer that they may start laying us off in the next month or so if things don't improve. 

From 2012 to mid-2019 it was again my primary residence at which point it was once again converted to rental property.At this point I must recalculate the depreciation since in the intervening years I made $50,000 of improvements to the property. 

Did they describe the improvements that were done in that section?

So I would suggest working on increasing your income, credit score, decreasing debt, increasing industry experience, etc. so that you improve your chances of getting approved by an underwriter as you work towards your goal of obtaining 20% down.