It's very feasible however it has a couple of things you might want to consider. Firstly someone setting up a custom address for you via vanity gen or vanity search simply means they are going to have the private key to such a wallet and it won't be safe to fund a Wallet like that. Therefore you have to run the vanity gen script yourself and off internet connection to avoid your private keys being leaked.
You also have to consider the fact that the longer the word's in the customization the longer time you have to spend running the script which would incure more costs like electricity. I have come across some reviews that running vanity gen on a PC isn't nice for the CPU health.