vinyl tarp: i have some car tents from costco (aprox $300) that appear to use a similar vinyl exterior and they hold up great (5+ years so far). I made one into a perm shed, but with that I added another layer of thick tarp on top (that also seems to hold up well, just make sure you use UV stabalized)
insulation: looks pretty awful to me. this thing is going to be cold in winter unless you keep the fire going 24/7
plants: good luck keeping these with enough light+water. watering these seems like a total nightmare given how any drips are going to ruin your structure/drywall.
foundation: anyone doing this, rent a (or buy a cheap) concrete mixer! I bought one used for $100 on craigslist. can sell it right back when you are done with the project.
flooring: "luxury vinyl planks" are awesome. I use the "lifeproof" brand (bought at home-depot) and they are great. completely waterproof, durable, and look like wood.