We really unable to tell you unless we know how much time you will have to spend on the development.

I just give you an example on how you can roughly calculate the cost:

Let's say you are now working in a full time job with about 40 hours per week (8 hours x 5 days). Your monthly salary is RM 4500.

Let's say you have the complete requirements and the flow, you estimate that you will need 2 weeks of time (or 80 hours) to complete the project.
Assume there are 4.5 weeks in a month.

Your rate per week is RM 4500 / 4.5 = RM 1000.
So, the project cost should be at least RM 1000 * 2 weeks = RM 2000.
But since this is a one time off project and they do not offer you any benefits such as insurance and allowance. You should charge more than RM 2000 (eg: RM 2500).

Don't be afraid to be taken advantage of when you are still building up your portfolio. You will learn from experience and increase your rate in the future when your clients trust you.

What database? The internal database like SQLite (preferred only for offline apps) or
at the backend web service which is using MySQL hosted in the PHP powered with
Apache server where Internet connection always needed?
Both are standard apps actually and most apps need Internet connection.