I don't need to prove how much both of us earn. Just show we have jobs in Hong Kong now and the annual salary. CIC not even asked me how to support myself, as I didn't declare my assets when applied.
There may have some tricks to fill the form. I just spent some money to hire a representative to handle the forms filling for me as I was too busy on my jobs, and it didn't cost me much. It's worth for me to hire a representative so that I could focus on my jobs at that time.