Here's my two cents on this. As Preferio said, don't! Now with that said that doesn't mean I hate MSP's. I own one and I love it! the problem is (and I found out a little too late) that basically what Mazda did was take a Protege ES and slap on a bodykit, turbo and paint it a bright color. The internals are the same as the N/A version plus the FS isn't known to hold up very well to boost. If you want a car to have fun in but not mod too much then fine, the MSP is ok. the cool thing about a turbo is slapping in a CAI and exhaust can seriously boost your HP and overall fun. The problem is when you start upping the boost, then you have a pretty good chance it will blow. I'm saying this mainly cuz you mentioned that your wifes pregnant and you know as well as I do that when your kids born then your costs per month is gonna go up. It would kinda suck for you to find yourself in a situation where you have to rebuild your engine cuz you decided to boost past 8PSI.
So bottom line:
Pros:
Great, peppy car for the price
Looks great and corners well
Turbo makes it easy to gain HP with mild modification
Cons:
The FS doesn't take to boost very well (will blow if boosted past 8PSI)
You'll be forking over extra $$$ for Premium Gas
Rebuilding the FS sucks (I spent $4000 on mine but that's cuz I went forged.)
Factory tune blows too, your car will run piss rich! Only fix is to get a piggy back or an aftermarket ECU.
After 250HP or so, your Tranny will give up the ghost too
Stock LSD sucks, causes torque steer and questionable handling when accelerating quickly
If you want a car that's fun, consider getting a Ford Probe GT or a Mazda Mx6 LS. I own a Probe too and let me tell you, at times that car felt a lot better than the MSP (164HP vs 170HP for the MSP but the Probe has better low end torque.) They're fairly cheap plus the KLDE will run just fine on all three grades so you can easily fill it with 87 Octane. If you want something newer and a Mazda, go for a Mazda 3 or 6. All I'm saying is, while the car is cheap up front, you'll end up spending a lot more fixing all the little issues and a few big ones if you choose to up the boost.