Wow, what a hard decision to have to make. It is a difficult question for anyone to answer without knowing the details.
Being an expat wife can be hard if you are not an outgoing person, so having depression will make it difficult for her. If you decide to come then you will have to be prepared to help your wife a lot during the first few months to settle in and get used to it all. She will really miss her family as well, that is one of the major things that you have to get used to being an expat living half way around the world from home.
Living in a house will be expensive here and can also be very lonely too, moreso than other places, well that is what I have found, but others may think differently. I think in a lot of way a
condo would suit you better as there would be places for your child to play and easy access to facilities etc, which would enable your wife to mix a lot easier than if in a house.
It is doubtful that you will find anywhere that has suitable rooms etc for a studio though as most places here are not that large and do not have garages at all. Then again this is only a two year stint you say, so perhaps you could put it on hold.
Schools are good here, lots of good places for your child to go, and I am sure that he will love it, if you get a maid she will have a network of friends who also have kids around the same age as well. Guaranteed.
The maid bit is a tough one too. Having a maid is not too expensive, but it can make life a bit difficult learning to adapt having a full time live in person thrown in to your life as well as well as all the other stuff. It is ususally ok for the husband as he only sees the maid for a short time each day, but for the wife, especially a stay at home one, well the maid is there all the time. It can be overpowering if you are not used to it, but also wonderful if you get the right one, you also have an instant babysitter for those times when you just want to go out the two of you. It can be easier to employ a part time person (a legal one I mean everyone) to come in and clean a few times a week rather than a full time live in one, but it may cost you more in the long run.
I do think that in your position it is going to take a lot of work from you in particular to help your wife settle in and not let her get into that depressive state of not wanting to do anything or go out etc. As germangirl said, it may just be the thing needed to bring her out and give her a spark. Perhaps find out before coming about things that are of interest to her as hobbies and see what is available here. Are you getting to come on a trip to check things out before you have to say yes or no? I am sure that seeing things up front for yourself would give you a much better idea.
Good luck with it all. You are obviously a very thoughtful person and going about it the right way to make the right decision. I hope I haven't sounded too negative, we really like it here, our kids love it here, it is a lovely place to live with kids.