Seven or 8 years ago I got a Kobalt brand mixer at Lowe's. I seem to remember about $180, but the website has it at a little over $280 today. Probably the same one, just 8 years of inflation. It has a plastic drum with 3 steel baffles inside.
Anyway, I have used it for over a thousand sacks of concrete and mortar over the years, and it just keeps going. One big secret of getting inexpensive mixers to last is that I used Locktite on every nut and bolt when I assembled it, even though it had lock washers. The common problem with lower end mixers is that the fasteners in the frame loosen slightly and they get rickety. Locktite during assembly stops that. This makes it take a little longer to put together, but is well worth the time.
I wash it out religiously after each use, since even a little old concrete will spoil a batch of mortar.
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Now, having said that, I think if you price out the ingredients you will find that, even with a short load charge, ready mix from a truck is less expensive than buying concrete in bags. Not to mention the value of your time and the backbreaking labor of mixing it. Plus, it is stronger and more uniform.
If you get 80# sacks of concrete, there are 45 bags required to make a cubic yard of concrete, and even at $125 for a yard with a short load charge you would need to get the bags at $2.78 to just break even. Lowe's in Southern Oregon, where I live, charges $4.41 per bag, which is the equivalent of $198.46 per yard. Home Depot only wants $3.65 per bag, but the ready mix is still cheaper. The economics of 60# bags are no better.
Around here, anything less than 2-1/2 yards has a short load charge. It is frequently less costly to order a 2-1/2 yard load in a truck and send the overage back than to pay the short load charge. Plus, that way I don't have to worry about coming up low with the amount in the truck. I can do the job in far less time, with fewer people, and it is a better job.
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A few last thoughts. If this is the only concrete work you are going to do for quite a while, get the ready mix and forget the mixer. Since you said you need mortar for block later, get the mixer and have it on hand. No matter how well you estimate concrete, sooner or later you are going to come up a couple of cubic feet short on a job. It is a lot easier and cheaper to mix this up from sacks you have on hand than to have to get another truck with 1/10 cubic yard.
When I mix concrete from sacks I usually add about a quart of dry portland cement from a sack before I start mixing. This greatly increases the strength of the mix you are making.
Any of the box stores will load 10-15 bags of concrete and a couple bags of portland cement in the back of your pickup for you. If you are careful with the bags and don't get them wet, you can return them for a full refund. This is great insurance for any concrete job when you have a ready mix truck coming.
Having enough rebar, and putting it on dobies or real rebar chairs is very important. Do not stint on this part of the job or it will be substandard forever. And, when you pour a footer for a block wall, or even the edge of a slab for under a block wall, you need to place rebar to go up the cavities in the block. If you don't know how to do this get some advice before you start. You can't put this in after the concrete sets. If you are building a stud wall on a footer or on top of a slab, you need foundation bolts. Again, have to put them in while the concrete is wet.
