You'll probably have to look up combos on a wiki. It's very poor design to expect people to guess combos, because most of the fun, challenge, and replayability is when you know all the combos and are trying to figure out how to mix them best. Kairosoft tuned down combo guessing on future games because of this.
Venture Towns is about property. On your first run, most of your cashflow comes from selling housing land. Your residents are dirt poor - they'd take a few years just to get to the $2k wage level. Though on a second run, you can import your starting resident with a lucrative job like Martial Artist ($6k) or Mafioso ($8k) and instantly start off with a decent cashflow. But otherwise, you'll have to live on housing and land price.
You make housing money in two ways:
- Initial Sale
- Rent Collection
Initial sales give you 6x the land price. That means you need to get your land price as high as possible before putting down a housing plot. Initially LP is $5k and gives you $30k. Put land next to a Nature combo and some trees, and it'll be worth $10k, giving you $60k. Land at well developed areas go for about $20k-$40k and thus sells at $120k-$240k.
Compare this to your residents earning money at a rate of $1k-$3k early on and you see how much of an impact this is.
Rent collections will pay you what the land is worth every year. The average will be a "house" or "condo", giving about 80%-100% of the Land Price. So, if you have about $200k of developed land, on average, you'll earn about $200k a year.
You'll want to develop these houses as much as possible - condos earn twice as much as bungalows and mansions earn 160% the LP.
Shops don't earn money
This is very counter-intuitive, but shops aren't there to earn you money. They are there to increase your land price.
Let's say you have only one bakery in the middle of town. Everyone will keep buying at that bakery until they run out of money. And then they'll work for more money and spend it. You'll want higher prices because they make people spend faster and work harder. But you don't actually want a lot of shops; each shop will lower the profits of other shops and
Some shops like the sports shops, college, trade school, arcade have such high prices that you'll lose money on them. Also note that the bigger your city, the higher their travel time, and the less time they spend working and spending money!
The 3x3 block
I took @Andy Fallon's answer and combined it for the 3x3 block, which I believe gives the optimal land prices and highest product price.
R is road.
H is for house.
2 are different combos.
T is a tree. Note on trees: The special trees will boost appeal. This is great for high paying blocks, bad for cheap blocks because they will appeal residents to buy cheap things instead of expensive goods.
Combos will boost land and product prices for adjacent buildings, and sandwiching them like this will provide double, stacking boosts for two different combos, and stacking land price for the houses.
You can also save a little space by reusing a item from two different combos. The following is how I set up my Geek and Toy combos together, giving enough space for an extra house:
G here stands for the Game Shop, a poor choice otherwise because of low price and high maintenance, but good in this case.
Don't be afraid to reuse combos
I have 5 business combos in my game, because of how effective and cheap it is, plus having offices nearby unlocks certain jobs and buildings. Reuse the good ones and don't even bother with the bad ones, like the Lunch Combo and Silicon Combo. I'm tempted to dismiss the Pleasure Combo because of its bad effects, but Casinos can earn quite a lot.
There's also another counter-intuitive game mechanic: The more research you do, the higher the research costs for the next item. It's tempting to research useless things like the lunch combo because it's cheap and you have too much RP to burn. This will bite you back later, when it increases prices of actual good buildings like the Art Museum and College.
Most of the combos are rather poor, but the game will throw different buildings at you in each play through. Some variety may be needed to unlock different jobs and such.
Business + Shopping
The business + shopping combo are one of the most important combo in the game because it unlocks one of the best characters in the game. Both actually go best in the same 3x3 block, because the 30% product price boost really helps with the Jeweler's high prices.
I've never unlocked the buildings needed for this early, but it should be your first target as soon as you reach Super Town status.
Use as few shops as possible. Maximize land price before placing houses. Set up special plants along roads for RP.