For me, saving 40+ min. every day on commuting is everything

especially you couple carpool. (double benefit!)

If "不过我们俩的收入在现在的自住房有rental income的情况下，付两个mortgage以及保持现在的生活质量是轻松的，能基本存下一个人的收入。",

then where is the pressure?

Yes, you would use up the cash for downpay, but you have two jobs for back up. Within 6m -1y, you would have piled up the needed emergency funds again.

This might be a great time, if not best of the best, to accumulate properties, as both price and rate are historically low.