This depends on what you mean by income requirement. If you are asking because you want to ensure your loved ones are taken care of indefinitely, then you want to choose a policy that simulates your yearly earnings primarily from interest. This is mostly based on what you earn per year. At 45 years of age your income requirement would need to be around $80,000 to $100,000 dollars per year in order for your loved ones to live hassle free. This way should something happen to you they would still receive your yearly earnings without depleting the initial payout.
If you are asking in terms of your present budget you have to look at what the monthly fee will be. Your income requirement is essentially whatever you can comfortably afford. The price of a typical quote for a healthy 40-year-old is usually around $100 dollars per month. So you need to be sure your monthly budget can handle around a hundred dollars in premium payments. This is also affected by the insurance company you choose. Each company has a different set of policy prices as well as ongoing specials. So the price may fluctuate but not by much. It is certainly not something you should wait to do.
Remember, the older you get the higher said premiums will be. This is because insurers usually operate on a 20-year-term. This means they expect you to live an additional twenty-years past the creation of the plan. Eighty is the latest age one can qualify for life insurance and the monthly fee for a $2 million dollar payout is around $8,000 dollars per month. Very pricey unless you already have a considerable amount of money. Fifty alone jacks the price up by $200. So do not wait any longer, forty is a prime age to take out a policy.