creating a custom entity which stores multiple bundles as per user input?

I want to create an custom entity(Lets say payroll entity) which has the following fields 1. Basic salary 2. Earnings 3. Deductions

It is possible by Entities

But now I would like to add some new feature

1. Basic salary(field)
2. Earnings(Bundle) contains (bun1, bun2, bun3 fields)
3. Deduction(Bundle ded1,ded2 and ded3 fields )

If a user wants to set his employee's Earnings and other details he can manual sets it .For an example if a user needs to set his/her employee's salary like daily allowance, travel allowance, bonus etc) he/she can do it from their own choice . And there should not be any restrictions for the no. of fields to add either bundles or fields . A user add custom bundles as well as custom fields.