Looks like the Harbor Freight 6x8. Here is a link to the page on the Harbor Freight website, where you can download the manual (with a parts list.) Also shows photos of the frame so you can compare.
Download manual for 6x8 Harbor Freight

I have the 10x12, so I'm a bit more familiar with the base on that one. The 10x12 comes with a steel base, but it looks like the 6x8 only comes with base plates designed to be attached to wood timbers in the ground. I'd inspect the base pieces to make sure they're OK. You can order parts from Harbor Freight for these greenhouses, but some parts are not normally stocked by them, and some are special order. I'd be a bit worried that something like base pieces might take a long time to ship to you. (Heads up, HF always used to tell folks it would take about three weeks to get non-standard parts, and six months later they were still waiting.)

In my hot climate the panels only last 3-4 years (less if not using shade cloth.) Those panels may be fine for years to come, but you can always order more panels if you need to (panels and clips are standard items and usually ship quickly.) You can get a quote on a whole new set of panels if you call Harbor Freight, if you're curious.

The aluminum frame in these is softer than the aluminum you buy at the box stores. Transport it carefully, the pieces may bend more easily than you'd suspect. It should unbolt pretty easily unless the previous owners got creative with some other kinds of more permanent fasteners.

I know some folks would say that these kits are so inexpensive that it would be better to just buy a new one, but I'm a scavenger/bargain hunter myself, so I can see the appeal of making it work.

Feel free to email me if I can help answer any other questions.
Building our 10x12 Harbor Freight greenhouse

Also, the panels are held in place with spring clips, but anyone who knows me remembers I'm a bit of a nutcase about adding at least one screw in each panel, through the panel and into the aluminum frame. Your mileage may vary, depending on your wind exposure, but my own greenhouse would absolutely not be standing (four years and counting) without these screws, and some interior bracing to add strength to the structure.

My blog above contains more info about my rantings about how to strengthen these greenhouses. (I like to sleep well at night!) ;-)

Mudhouse thank you for the links. Your greenhouse looks great! I really like how you took the time to document the assembly of the HFGH and all the extras you put into it. I will be using your ideas on how to reinforce it. I live in an open area so it gets really windy here. I will probably use clear silicon also to seal the panels in.

I picked up the greenhouse today it is a HFGH. I ended up taking it somewhat apart . I took the roof off leaving rafters attached to the top ridge and separated the wall sections. Not much to put back together. I'm just using it to start my seedlings in the early spring.
Thanks again for the info!

Looks great! Where did you find a steal like that on CL? I live in AZ and search almost everyday. I wish I could find something like that!

When I'm looking for something instead of just searching CL I put a wanted ad. I put the ad in the Farm & Garden section. I had many replies.

Here is the ad I put.

Looking for Hoop House & Greenhouse Frames

Looking for metal hoop house frames. We will dismantle your existing frame work. We will take any size small or big. Please email me the size of your old hoop house or send a picture. Also interested in Green House, Carport frames. Will take in any condition. Prices will vary on condition and size.

I also googled some pictures of Hoophouse & Greenhouse frames and put the pictures with the ad gives them an idea of what I'm looking for.

Going to look at a Hoophouse frame next week. It's a 12x24 metal frame looking to get it for under $100...:)

I siliconed mine, but a couple of them still ended up somewhere in Kansas. :(

For ANYONE looking for a greenhouse (or anything else for that matter) on CraigsList, I discovered a WONDERFUL tool called "List Alert". They search for things on CL for you! Just go to their website, type in your CL area you want to search and type in the item(s) you're looking for. Whenever it comes up for sale, you get an email telling you about it! I just missed a HFGH last week because it sold the same day. But, I got my white donkey and my silkie chickens this way! And ever searching for more 'treasures' this way on CL

Thanks, I never knew that existed. Looks like it would be very helpful (I never remember to check CL often.)

Here is a clickable link to the site.
List-alert.com

Unfortunately, List-Alert is no more. I LOVED this site and found many hard to find items by using this search engine. I heard CL sued them, which is stupid since it brought many sales to their customers. it...was....AMAZING!!!

I got an old frame like yours with most of the panels on CL for $50. I made a wooden base of PT 2 x 12's and fastened the greenhouse to that. When we have a storm, I just open the door and take out a few panels on each side. This lets the air move through and has worked for every storm we've had in the last three years. I only heat mine for a few weeks in March for starting seeds. I throw a large piece of recycled bubble wrap over it at night like a clear blanket.It has been a ton of fun for a low price.