This is a subject that comes up fairly often, and opinions vary widely.
I'm in agreement describner with regard to the Kenmore. I have owned and used a walking foot industrial machine, a Sailrite, and I collect sewing machines from the 50's and 60's (primarily Japanese).
I agree that a walking foot is desirable, but depending on the complexity of your Sunbrella project, you can be well served with just about any domestic machine made in the 50's and 60's. But, that doesn't necessarily help a newbie pick the right one from Craigslist.
To simplify the process, I would suggest you look at any Kenmore with a model number prefix of 158. Example: 158.1802. Additionally, make sure it is one of their machines made in Japan, not Taiwan. The Craig's ads usually don't give the model number, as the sellers are usually selling grandma's old machine, and they don't know or care. Or, they might say it's a model 64 because that's what it says on the manual, but the model number on the plate on the machine says 158.160220. So, ask. There are many brands and models that will serve you well, including Singer, Pfaff, etc., but I suggest the Kenmores as they, IMHO, sew as well or better than anything out there, and tend to go for less money. Most of the Kenmores have at least straight stitch and zig-zag, and many have built in cams, or accessory cams that allow you to do decorative stitches. For your Sunbrella projects, all you really need is straight stitch, however zig-zag may come in handy for other projects. Oh, one more thing on Kenmores..the 148 prefix machines from Japan are nice too. Typically have fewer frills, but still very good.
99% of the Craig's machines need servicing immediately. Don't run it until it has been thoroughly cleaned and lubricated. You can do it yourself if you're meticulous. Plenty of info online about the process.
I used a Kenmore to make a mainsail cover for my Catalina 28, as well as a boom tent, front hatch rain canopy, and a case for my chart book. I'm sure you can find someone who has made a dodger with a domestic machine, but I wouldn't do it. The limiting factors with a home machine are the inability to use larger needles which allow for heavier thread, less power, and no walking foot to feed the fabric more effectively.
I like the Sailrite machines, and I like the Sailrite company. Online arguments over wether they're a good machine can be fierce, as they are dismissed by some, and considered overpriced by others who advocate buying very similar low priced machines from other companies (less than half the cost of Sailrite). I would steer you to the Sailrite for a variety of reasons. Emphatically. If you get one and decide you don't like sewing, you will have no problem selling it for a good price. It's ready to use as soon as it arrives, and you have excellent customer service from Sailrite. Check out all the instructional videos they offer for free. We're lucky this company exists, as there is no other like it.
If you get a Kenmore and don't like it, you'll be able to sell it for what you paid for it, but you'll have to go through the cleaning and oiling process, and there is a small risk that there is something wrong with the machine that you can't fix. Expect to pay $75 to $100 for a good Kenmore. If there is someone in your area that sells them in serviced condition, maybe as much as $125, but how do you know if they did a good service? It's not hard, you just have to take your time and be meticulous. It's common enough to find a 158 series Kenmore for $20 to $50 on Craig's, or even free. Some come with tables, but all can be used as a portable on any table top. Typically, the machines that come with a table sell for about the same as the machines without a table.
One last thought. A domestic Kenmore from the 60's to early 70's is a very well made machine. Well designed and engineered, good machining, good motors, well finished, and smooth running. My 158.1802 machine is my "go to" machine and is a joy to use. Made in 1968, and will likely run fine for another fifty years. The Sailrites are more crudely made with rough casting, less attention to detail, noisy, and not as smooth running as a Kenmore. Basically, kind of clunky, but more capable of handling Sunbrella, and have a service life of 50+ years of home use with proper oiling.