how level does the land need to be?

Hi everyone. Getting ready to start a gothic arch hoophouse, about 60 ft long x 20 ft wide. My wife is from Thailand and we will be using it for growing Thai vegetables/fruits. The question I have is how much slope I can have over 60 ft? Should the hoops be straight up and down or tilted slightly to accommodate the slop? I think I've got about 24 inches slope over that 60 feet.

Depends on how much you like to walk on a slope. For a hoop house, it might not be a big deal but for a kit GH, it is a big deal as the foundation is what the struts rest on.

I had a 14x18 GH that we cut into the ground at one corner by maybe 10 inches and at the other diagonal corner we used gravel to build up at least 14 inches to make it "level". The pressure treated 6x6 lumber posts were easy to anchor in with 18" rebar. When the kit came in, it made assembling it so much easier making the foundation level and square due to the prep work.

My parents came every weekend for several weeks involving this GH. My dad was the master of leveling due to his work with the lake installing campsite picnic tables and RV pads.