Thank you for the posting the question.
Sorry, can check if you are a Singaporean? To buy a resales HDB flat, you must be aged 35 years and above and single (ie Unmarried or Divorced.)
There is no income ceiling unless you are applying for CPF Housing Grant and/or an HDB Loan.
Hence, you can apply for a HDB housing loan as long your gross monthly income is $3000 and below.
For the CPF grant, are you buying the flat to stay yourself or with your parents? A single who buys a resale flat under the single scheme gets a CPF grant of 11K.
For the Higher-Tier Singles Grant of 20K, the parents must be included in the application as the co-applicants or occupants.
For cash over valuation, the amount you will be paying will be subject to the type and location of the flat.
If you need further assistance, do feel free to contact me for a non obligatory discussion.
We hope we can help you answer your queries.
Have a nice day.
Desmond Chan 9819 7201