Yes, happy days are upon us with legalization
This is a great bang for your buck. I've got one of these 10x20ft, but it only has 8ft of clearance at the center purlin (meaning the side/shoulders have about 6ft clearance). So if you plan to put plants in their the entire summer, you'll either have to train them like crazy or just put them in there beginning of July so they never get more than 5-6ft tall.
Also comes in 10x10ft if that fits your space better:
Canadian Tire has the 10x20ft on sales every 2-3 months sometimes as low as $300. I don't see them on CT website, but I got 2 in stores a year apart for that price.
The plastic is opaque, but last only about 3-4 years before the edges start to wear (I recommend taking it off in the winter for sure). The bottoms roll-up and has front and back peak vents, which provide great air flow on hot days. I would recommend putting 2 circulation fans in each opposite corners and hang box fans in the peak vents for even better venting (https://www.homedepot.ca/en/home/p.2...000682449.html
You'll probably need 30-50% shade cloth to get through July-Aug if you want the temps below 30C (with shade cloth and box fans, you should be able to keep it slightly cooler than outdoor temp). I use to live in Ontario/Quebec and now farm in coastal BC, so I can promise you that Ontario has substantially HOTTER and more humid summers than Cali or BC, and obviously way more humid. I've used the 10x20ft for seedlings and use 70% shade cloth in BC to keep it below 26C, but we don't have more than 10-20% humidity until mid- to late-Sept.
If you were going to go the DIY route, I recommend buying a tempo/car garage from Costco, they are only $250 for a powdered steel 10x20ft (the model I got was in-stores only). Use that steel frame rather than PVC or bending EMT yourself because it's designed for snow loads and cold temps. You can build your own shed base or cinder blocks perimeter to give it extra heights. You'd have to source your own diffuse
greenhouse plastic, which could be tricky if you're not a farmer willing to buy +150ft of it. Lots of youtube videos on how to build your own roll-up sides too (https://www.youtube.com/watch?v=2GyYAnsyuLc
). And if you want to go crazy, you can get vents like this for your peaks: https://www.johnnyseeds.com/search/?q=vent&lang=en_US
The money you save on poly-carbonate would certainly be better spend on automatic peak vents. You can also use 90% privacy screen/shade cloth along the sides, so you can roll-up the sides completely and still nobody would be able to see into the inside, while keeping great airflow.