Need help with coding a custom personal finance application (website)

DELIVERABLES
Primary Goals of Software/Tool:
*Compute compound interest for both home loans and Investments
*Be able to track and use this information throughout other portions of the code.
*Net worth
*Be able to setup Net Worth goals 6 monthly
*Be able to track net worth worth monthly/tracking towards goals above
*Be able to determine trending issues (i.e. $50 of goal for last 2 months, you
are at risk of missing goal)
*Be able to forecast (i.e. What would happen if interest rates changes to X on Y, or what happens if Shares on average slip from 5% to 2.5% or inflation changes from 0.5 to 2.5)
*Be able to work out tax for pay (i live in australia), i currently use a website (https://paycalculator.com.au/) its awesome.
*I also work what i call side hours (basically additional work), i would like to be able to set a budget), i.e. i earn x per hr (and i want to have Y after tax per month difference between what i get normally and post side hours (overtime). There should be a place i can do this.
*Super (Australian retirement fund basically), i would like to be able to track how much goes in, current balance, and overall return in selected Period. I would also like in all cases to be able to extrapolate this over any given period of time. (i.e. average return over 5 years is X, and therefore assuming same input of money and average return of X, you would W in 5 years.
*Happy to provide more information… if this job interests you, and if the work fits within my budget.
*Also i am very security focused, given this is allot of my job. So this will be key in terms of any stored data or alike.
*I am happy to input values each month for network (i.e. no live bank feeds or similar required)