Here's the best money-making strategy I could work out:
Forget about trying to keep your rating high at all times, it's much better to alternate high-rating weeks (when you make money) with low-rating ones (when you farm rating). They key is that at minimum rating, you only get two customers per day, and their ratings get added rather than averaged. It goes like this:
Week 1: Buy two of the cheapest peegs you can, F-rank if possible. Crank the price up as high as it will go (you can click the number and mash number keys instead of clicking/holding the arrows) and get through the first week manually matching peegs to customer preferences as best you can. Buy additional cheap peegs when you can; don't worry about going into debt at the end of the week due to maintenance, we'll make it up in week 2.
Week 2: Your rating has improved, and you have far more customers. Crank the price up and get to work. Maxing out the price carries a hefty rating penalty, which is exactly what you want. Don't bother matching preferences this time; if anything, you want to get the minimum rating. You should have about 4 peegs and 8K in the bank at the end of this week.
Week 3: Your rating should be at 1/2 star again. Set the price to 0 and match preferences again. Since you only have a handful of trash peegs with low upkeep, you have more than enough money to run the house at a loss for a week. When the price is zero, even a complete mismatch in an empty room gets you a 5S rating from the customer, and as I said at the start, the ratings from your two customers get added together rather than averaged.
Week 4: Your rating has skyrocketed, and you have loads of customers. Crank the price up, buy a few more cheap peegs, and get to work. Once you have 24K, unlock the first Secretary achievement and hire an S-rank counter girl to automatically assign peegs to customers. Whew, much less clicking!
Subsequent weeks simply repeat steps from weeks 3 and 4. Buy additional trash peegs and counter girls as needed. F-rank is all you will ever need (except for achievements).
Some additional info:
Your peegs can handle more customers per day as they level up, so there's no need to go on a shopping spree. It's okay for some customers to go unserved; your rating will suffer, but that's a good thing during weeks with loads of customers.
You can upgrade rooms with furniture to increase customer ratings. Since you only care about ratings during low-rating weeks when you only have two customers, you only need to upgrade the two rooms on the right (counter girls assign rooms right to left).
Counter girls come in three ranks, A, B, and S, able to assign 5, 10, and 20 peeg-customer pairs per day respectively; there's no point hiring the lower ranks. Clicking the plaque on the front desk de/activates counter girls, in case you want to assign peegs to customers manually.
Clothing is irrelevant and a hassle; as far as I can tell, there's no way to automate its purchase and assignment to peegs.
For some reason, at max rating, price is capped at 400 rather than the 1040 of preceding ranks. So don't overdo it during your low-rating weeks; for optimal profits, you want your rating high but not max.
