I did four 12X25 pieces to make my driveway double wide beside the garage. I did all that about 20 years ago and did all the work as mentioned above with two friends. Not the same two friends each time though - now they don't answer the phone when I call.
I did the slabs to park my motorhome and trailer. All in all, the front two slabs have held up very well but the third slab where the motorhome parks all the time has broken up somewhat. I did four inches of concrete and probably should have done six inches there with additional reinforcement.
In those days, concrete was only about 27 dollars a yard so each slab was reasonable. The prep work and labor was free (excluding beer and excedrin) but you really abuse your buddies when they aren't used to it.
Beside my latest garage, I put down about 10 yards of 3/4 inch gravel to park my open trailer and a couple cars. Even compacted, it seems too fluffy for me to consider using as a motorhome parking area.
I've done the ready-mix trailers with a yard bucket for shed slabs and they work well but aren't good for a larger slab.
I've also got a couple old Sears mixers and will do stairs and sidewalks on occasion but usually stop at about a half yard now (5 loads). Carrying sand and gravel in 5 gallon buckets isn't as easy as it used to be.
Hire the pros to do your slab.
Chuck