Hand pumps/beer engine????

[beer gut]

Hello everybody i hope you are all well. I realy want to buy a hand pull/beer engine for the summer bbq's, however i have no idea how to set the beer engine up or how to work it.I don't realy know what to look for when i come to buying one caus some come reconditioned and some don't. So any advice on how to set up a beer engine and to use one would be much appreaciated caus i don't wan't to fork out 60 quid and then not having a clue how to use it.