Here's what I know
There aren't any airparks in Houston that are selling lots, unless you count Miegs, which doesn't seem to be going any where. But you might be able to find a house or lot that someone is selling if you wait long enough. I looked for a couple of years and never find anything I liked and could afford.
By the way, the South vs Northwest thing is a matter of liking where you live vs. short commute. Personally, I put up with the commute from Cypress (NorthWest on 290) because I like to live in the woods. North of I-10 is piney woods. South of I-10 is scrubby prairie. However, southeast around Friendswood and Clearlake is pretty (big live oaks and spanish moss) and close to the water. The other thing to consider is that when a hurricane comes, you have to think about evacuating if you live south of I-10, especially in the Clearlake area.
Knowing what I know now, if I was moving to Houston again I'd look Northeast around Kingwood and keep my plane at Williams airport in Porter. The commute to downtown from Kingwood is under 45 min. and it's in the woods and close to Lake Houston. That is, unless I got lucky and found something I could afford at Dry Creek, Polly Ranch, or Covey Trails.
Here's the list, best I know.
Miegs. Far northwest. A couple of miles south of FM 2920 on Muschke Rd. Supposedly under development but there hasn't been any progress on it in about a year. They were asking $90K/acre last I heard. At least 1.5 hours to downtown during rush hour.
Dry Creek. Nice, small upscale airpark Northwest in Cypress, a couple of miles north of 290 on Skinner Road. Turf runway that's like a golf green. Sold out about 4 years ago but occasionally something comes up for sale. About an hour to downtown, but there's a commuter bus terminal close by.
Hooks Airport. Northwest, near Tomball at Stubner Airline and FM 2920. This is a large, towered executive airport where there are many residential live-in hangars. There are no lots available that I know of, but occasionally someone sells their hangar/home. The airport is privately owned and rumored to be up for sale. LONG drive to downtown because no freeway goes close to it. Probably 2 hours.
<< update -- I was at Hooks this morning to help a buddy with his first flight (way to go Jim!). There's a hangar/home for sale facing the runway and next to the seaplane strip. 7844 Eagle Lane. 281-794-3570 >>
Skydive Airpark (or Skylake, depending on who you're talking to). Far Northwest, near Waller. South of Highway 290, on Mathis Road. There are usually several lots or homes available from owners. It has a lot of potential, but also a lot of political problems with both the golfers (it's also a golf community) and the runway owner (who owns the skydive operation), so the place has a kind of trailer park feel to it that turns a lot of people off. But it's pretty cheap. 1/2 acre lots usually run low $20's. It's a REAL long way to downtown. At least a 2 hour commute.
Sport Fliers. Nice little airpark on the prairie west of Katy, where my EAA chapter meets. A couple of miles North of Brookshire and I-10, on highway 362, at the crook in the road. I can't think of any separate homes. Most people live in their hangar. It's a turf field that I've always disliked because it's rough and tends to flood in the middle. There's usually a lot or two available for sale by owner. A long drive in rush hour, probably at least 1.5 hours.
Covey Trails. Beautiful, very upscale airpark with a wonderful turf runway. The lots sold out about four years ago and I've only heard of one place for sale since. Its south-east of Katy, in Fulshear, at the crossroads of FM 1463 and FM 1093. About an hour to downtown.
West Houston Airport. Nice uncontrolled executive airport in Katy, a couple of miles north of I-10 on Barker-Cypress. Hangar lots are for sale, but high as a cat's back (I think he's asking $150K for a 1/4 acre lot). You can build a live-in hangar but not a separate house. Read the contract carefully, though. There were so many restrictions and disclaimers when I looked at it that it seemed like just a fancy way to lease you a lot and also stick you with the property taxes. I love landing there, though. The runway's so soft it's like landing on a pillow. Some kind of special asphalt.
Polly Ranch . Older upscale airpark with paved runway in Friendswood, at 528 and 518. 45 minute commute. You could be neighbors with the famous Paul Dye!
Wolfe airpark. North of Manvel, near 288 and highway 6. Lots are sold out but there's usually something for sale by owner. Kind of run-down. Probably a 45 min. commute
Waverly Estates. Way up north in New Waverly, even north of Conroe, and east of I-45. Upscale airpark on a prairie. Turf runway, kind of rough. The commute is probably over 2 hours, but I believe they are still selling lots.
Lake Water Wheel. North-East of Cleveland in Shepard, about five miles east of US-59. Another very long commute, at least 2 hours. It's an older airpark and sold out, but there are always rumors that new lots are going to be opened up. It's a modest neighborhood. Most of the hangars are live-in, but there is an adjacent residential neighborhood where some hangar owners live. The 1/2 acre lots when they come available are real cheap. I know of one that sold two years ago for $5K.
Songbird . I've never been there but on the sectional it's southwest of Alvin. A couple of years ago they were selling 5 acre lots.