Put in the hard work now and build a solid foundation and the business will come.

I think the margin might be too thin on this one, unless you can get it inspected and estimated and put in a good low offer that gives you a cushion.If you're looking for a first time flip, I would recommend doing some legwork and either drive-for-dollars or put together a mailing list. 

We are considering partnering with a neighbor to purchase off the grid lakefront land, renovate the run down cabins, put in solar and vacation rental the cabins. 

I've spent ~$200 on ads, generated ~10 leads and put in ~4 offers.

He's paid:1 - What ever cash he originally put in plus...2 - What ever losses he's incurred over the time of ownership (this would be "zero" if he's cash flowed the entire time, plus...3 - What ever he still owes...in this case $38,500.Since everything else is profit (cash flows), all he really has to do is sell it for more than the total of listed items 1 - 3 above, and he makes a profit....cash flows plus difference of what sells it for and what he paid (items 1 - 3) for it.This is one of the unappreciated advantages of owning rentals instead of flipping.  

Is it realistic to think that I can get a heloc on it to purchase a rental and put in the trust?

I think a lot of contractors get distracted with what they have going on currently and forget about getting future work.  

Those deals that do not follow your criteria, are what I call "shiny objects of distraction".Having said that, that doesn't mean you can't have more than one set of criteria, and you should, simply because you should have more than one exit strategy that you analyze every property for.  

It's much easier to put in carpet and, if the future buyer requests it, change it to tile later.

But if you need to put in 20k-30k, then that's pushing it and there's not much value to add.