Habaneros getting me a new greenhouse.

I bet you never heard that before.  I always wanted a greenhouse. My daughter bought me a metal and plastic one that I enjoyed. Then the plastic ripped after only one year. I used wood to make a frame around the bottom, and redid the plastic.  I live in N. California, (a greenhouse is an indulgence) and don't have lots of money, so I feel I must keep the cost low. The plastic I used was just wrong. It was redone in February 2021, and the sun has already split it.  I ordered greenhouse plastic this time.  I was talking to my son, saying I needed to get in gear and redo my greenhouse again because I want to see if I can keep a tomato plant and a couple of peppers alive through the winter.  
I bought a habanero pepper on accident this year ( we aren't spicy people) My son is crazy about the habanero.  Now he wants to build my a greenhouse for the habanero.  It won't be fancy, and unfortunately we can't swing real windows. I do have dreams of refurbished windows someday.  But it will be a more real, and substantial.  I have already had to pull him back.  I only need a small greenhouse.
I'm open to suggestions on design.  It only gets below freezing a few times a year.  Mostly I use it to try to over winter a few plants, and get an early start on veggies in the spring.  Even in spring my other greenhouse would get super hot, so I'll need some ventilation.  We need to keep cost down.  It doesn't have to be fancy, but I would like it to look nice.  
On a side note I was wondering about digging into the ground a couple of feed.  
I just wanted to share this because I think it's funny my son is so determined to keep the pepper alive. I did suggest we dry and grind it for future use, but he wants to use it fresh.

Overheating is a big disappointment. Would it be possible to remove the glazing for the whole summer and put it on for winter? That's what I do. Plus open the door and a window for cross-ventilation in the shoulder season when the glazing is on but days are too hot, nights are cold.

I want to reply not about the greenhouse but about the motivational impact of the habanero.

I think this is awesome. Really really awesome. One of the big challenges I see is figuring out how to get more people to become actively engaged in permie activities. For your son it was a habanero. Maybe for my wife it will be our apple trees... I don't know, but if we can figure out what gets people excited to engage we have less work to do ourselves and everyone wins!

A candle flame is not diminished when used to light another candle! Or something like that.

If your goal is just a place to overwinter plants, +/- early spring seed starting, I suggest you look at the style of The Chinese Greenhouse. https://permies.com/wiki/143395/Chinese-Greenhouse-Dan-Chiras
Insulating the north wall and all or most of the east and west walls will may make it much easier to keep it warm in the winter fairly passively, so long as there's some thermal mass inside the insulation.

Thanks all.  I like the idea of being able to remove the glazing, but I'm not sure how I would pull that off.  I did see a greenhouse that has panels on the roof that lift, and I hope that will let out the heat in the summer.

My kids always loved playing in the garden as they grew up. Now that they are adults it always makes me feel good when they take an interest in the garden, or other projects on my endless to-do list.  They are all very good at reuse, recycle, and repurpose. When one of them helps me with a project, it's more fun, faster, usually turns out better, and means more.

I read lots of greenhouse posts on Permies.  The Chinese greenhouse is super cool. I would love to do something like that, but it just won't work.  Our property is totally flat, and we only have.99 of an Acer, and on that are a house, mother in-law house, a large barn, and two little sheds. So there just isn't the room or topography for that.  I wanted to dig into the ground 3 feet. I thought this would help stay warm in the winter, and cool in the summer.  The down side of getting help from my son is he tends to take over, or at least try anyway.  I just can't seem to convince him it's worth the effort.  So it looks like it will be a traditional greenhouse.  That's ok with me.  Especially since he wants to make it so he can move it with the skid steer.  If he pulls that off I can still go underground in the future.  

I'm looking forward to this project. I'm also excited to experiment with veggies that don't normally survive the winter.  Wish us luck.

How big is the pepper plant? Can you pot it?

I bring mine inside in the winter... tehy fill up the house but they do survive... just a thought .

also i made 2 greenhouses out of old windows.. .they are pretty rough n' tumble but the do the job - i put an intact opening window on all 4 ends and built them with shed roofs (one slope)  - the high slope side i "unplastic" as soon as the frost is gone i leave open all summer - vents pretty well.

hope this helps - cheers!