This is going to make me unpopular - well, more than I am already, I imagine - but,
my solution is to do... nothing. I have basses and guitars of all types, that have been in the house here with me since 1990, and they seem to be just fine. According to the US government weather websites, the relative humidity in Las Vegas runs from a low of 13% (June) to a high of 40% (January), for an average of 27.7%. When I get a new bass/guitar, it takes a week or 3 of sitting out on a stand to get it acclimated. Then, I tighten all the screws and whatever; do a set up on it; and it's good to go. Usually stays that way, too. Fret boards do tend to get a little dry, but that's easy to deal with. Other than that? No problems so far...
So, should you do what I do? Lots of people here will tell you "Oh GOD, no!" But, that's up to you. Personally, I have no desire to create a micro climate in my house; spend a lot of time maintaining it; and have a bunch - and I do have a
bunch - of "Bubble-baby" instruments that can't leave their room, lest they dry out and blow away. But, some folks do... As for humidifiers themselves? Yes, they are maintenance intensive and a PITA. Your other alternative might be to install a swamp cooler. There are a ton of older, cheaper houses here in Vegas with them, and they do work pretty well. And, judging by all the rusty tools in my friend's garages that have a swamp cooler on the roof? They keep it pretty humid in there, too ...