Hey GD Plastering.
If you are doing lots of your own work like extensions, new builds, bit of site work etc etc anything where you are using a lot of material regularly all you need do is swap the materials you use for ones that go through a machine. then a machine can be used regularly by yourself. For eg if you were render and setting a house you can buy CPI motor at about 3.75 a bag and pump the backing coat on. Same goes for any job you got just make enquirers about suitable material replacements. a quick post on this forum is usually all you need. There plenty of machine users on this forum and if you browse the forum lots of them need help from other machine users.
If you are doing small jobs like the odd ceiling or overskim etc then buying a machine is a waste because it wont be needed on them jobs, if you have a well used whisk, and a well used belle type mixer then a plastering machine can only help if used properly.