fleas are the leat of your worries, what about the life of slavery you are about to enter, you will either be getting up to let him in or getting up to let him out unless you fit a catflap. you will have to get used to using your laptop with a cat on your lap. not impossible but not ideal. you will have to get used to being woken up in the night with either a cat jumping on the bed demanding to be fed, the cat creeping onto the bed with the stealth of a red indian and curling up next to your ear in total silence and then purring at full volume and waking you up thinking there is a motorbike in the bedroom. you will have to endure visits from friends and family with the cat demanding your undevided atention throughout and making you seem like a person of feeble mind under the control of your cat master. there will be no more extended shopping trips unless you want to return home to the angry stare of death that signals your bosses displeasure because you went past the scheduled feeding time and forgot they cannot use a tin opener. you will experience the inadequacy you are made to feel when you call the cats name and they look the other way for just that little bit too long and appear deaf until they turn their head slowly and look at you as though you are annoying them and then they blink at you, just once, and yawn, signalling that you are nothing to them but an inconvenience. worst of all, you will be the recipient of various inavcapacitated small wild creatures that they will deliver to your feet for your to eat and enjoy but also kill as they believe you desire that pleasure yourself.
but do what you feel is right, personally i would keep him, he'll never let you down,