It would be best if you can get a In-principal approval by a bank on your loan limit. From there, you can estimate how much cash you would need up front and the max price you can buy.
The practise is, First 5% cash, next 15% cash and/or CPF. Thats assuming you have 80% loan.
As for the amount to be deducted, it depends on your age. it would be best to check with CPF board regarding using your CPF for your next property.
DO give me a ring if i can be of any assistance.
CEA Reg: R012218E