Hi, I am thinking of investing $500 every month. What are some good options for investment? My goal is to start saving for retirement as I’m nearing 40 but it’s better to start late than never right?

Great work on starting! For beginners, I'd recommend starting with robos as they're passive (on your end) but actively managed (by seasoned investment practitioners).

You have to think about your risk appetite. For a safer approach and passive investment, you can consider roboadvisors. I am using StashAway for US/Europe ETFs and DBS digiPortfolio for Asia ETFs.

Accumulate once every 3 months and put it into a S&P 500 ETF quarterly! The historical returns are 10% and I would say it is much better than saving bonds

I don't think investing $500 every month is a good tactic. I rather save the money and keep it in cash and invest when market price is low. Your return will be much higher if you buy low-sell high, rather than investing every month.