These companies can help strengthen your long-term portfolio.The stock market makes it easy to build wealth. All you have to do is invest in strong businesses that are growing and profitable. Choosing top stocks from among brands or services you use regularly is a great place to start.To give you some ideas, three Fool.com contributors are here to offer three timely stocks to buy in September. Here's why they chose Apple (AAPL -0.19%), Airbnb (ABNB -0.01%), and RH (RH -1.55%). 1. Apple still has an ace up i ...