Really depends on what you consider easy. For me, nothings is easier than snakes. Don't need to be fed daily, cleanup is only needed as often as the eat for obvious reasons, and if you get a species with no humidity requirements, you don't need to be around to mist. Inverts are another option. Tarantulas can be kept at room temperature if your house stays in the 70's, fed weekly depending on age, and some don't need high humidity. Scorps are easy too but most require heating. One cool often overlooked option would be madagascar hissing cockroaches. Feed em carrots or other produce and you can go away for a while and the will self sustain pretty darn well. They do require somewhat high humidity though.