Re: Retirement account and buying car
..... You are right I am not an expert in this field. .....
Nobody is perfect and I don't hold it against you. There is no use of haggling over made up figures.
People who set up and manage these plans do it for living and do it for a fee. If you want to work with me, then PM me and I'll give you the fee structure.
However if you want to work with someone else in setting up 401K, then you should consult a tax adviser and a financial adviser. Pay them their fee, give them your financial data, your risk-tolerance and they will surely provide you with a complete plan for savings.
Then you use whatever fiqh you have to calculate zakat (and in some cases Khums) on it.
But I urge you to quit giving "fatwas" [religious opinions] as to what is haram and what is halal based on very little understanding of the topic. It is unIslamic and immoral to give someone incorrect advice.
Peace and love to all,