When you use idioms, it makes you seem more friendly, because idioms are usually informal.
Most people who live in this area are very well off.
“Very well off” means they have a lot of money.
The people who live here are very well-to-do, you can see because they have a very big house and two cars in front of the house, a Mercedes and a Lexus.
Well-to-do also means that they have a lot of money, and is the same meaning as rich, and well off.
Well-to-doはお金をたくさん持っているという意味でもあり、rich, well offと同じ意味です。
He spends money like water. Last week he bought two new suits and then he bought two tickets to a pop concert.
When you spend money like water, it means you spend a lot of money and you don’t worry about it.
We have to tighten our belts because we didn’t sell a lot of goods last month, so we don’t have a lot of money this month.
Tighten your belt means you have to spend less money than you did before, because you don’t have enough money.
Tighten your beltとは、お金が足りないので、以前よりお金を使わないようにしなければならない、という意味。
He bought a lot of stocks when the price was very low, but the price of the stocks increased a lot over the past three months, and so he sold them at a huge profit. He made a killing.
When you make a killing, you make a really good profit on something.
My dog-walking business was quite a money spinner when I was at university.
A money spinner is a successful business or a successful way of making money.
A money spinnerとは、成功したビジネス、または成功した金儲けの方法のこと。