If it's as wet where you are - Snails, sell them to local gourmet restaurants...
Love the sound of the mini-mule! Or if you like equines, you could get some Icelandic ponies or other near-primitive type. (Might appeal to zebra-loving granddaughter

)
Kashmir goats and sell the combings to handspinners....

A pair of camels? (Lllamas and alpacas are too common now.

) Again, you can sell the fluff.

I hear somewhere is staging camel races...
If you've a pond, exotic birds? Flamingoes? (No idea about conditions they'd need, just flinging out mad ideas now.)
Anything,
anything, other than cockroaches. Eeeeiiiuuuwww. (Sorry Alistair - but eeeeiiiuuuwww.)