The world need can be literal or figurative. It's definition by nature depends on the person using it. No matter your definition, what if all your needs are not met. You've figured the budget, done the math, and you still need more money. Now what? The way I see it, there are three choices-the after retirement job, the after retirement small/home business, and playing the market (although some might say the latter was a job). While I won't comment on the day trading aspect, both of the other two options have advantages and disadvantages
Many folks find getting a part time job a solution. Part time work outside the house has its advantages. It gets you outside of the house, if you have that need. it can be a chance for socialization as well. Assuming you have a regular weekly schedule, the amount you will receive will probably not vary much from week to week. Income will arrive in a couple weeks, as opposed to a small business which has a start up delay both in terms of money and time. A part time job will probably not cost you much, other than commuting costs. On the other hand, when you have a part time job, you gotta be there. Some flexibility is lost. You may be reporting to people younger than you, and you will be low man on most of the proverbial totem poles. Last but not least, I would simply observe that as retirees, most of the jobs we take are those that traditionally are taken by entry young people. If we need those jobs, what are we expecting them to do.
The biggest advantage of self employment (usually but not always done at home in retirement) is the freedom of control-of our time as well as other aspects of life. Obviously if you are in anything related to customer service, you will have appointments to be kept. On the other hand, most of your schedule is up to you. So if you wish to spend the day on the patio with a book, life as you know it may not end. A small business may be more fulfilling as it is most likely to be a hobby or an interest that you have developed further. A small business can keep you close to home (a double edged sword, I know). The biggest downsides to self employment are irregular income and the need to develop a customer base before you see a profit. Most small/home businesses require investments of time, money or both in the start up process. While there are some service business that bring in money immediately, few of us are ready to mow lawns for instant cash, if you get my drift.
Obviously, before looking for second income, you should reevaluate your expenses and financial position. Downsize as much as is humanly possible according to your comfort level and financial needs. Ideally, the second income should be used for wants, extras that make us feel less deprived, rather than for needs. Know how much you would like to make, as well as how you will make do if the job doesn't work out or the business doesn't succeed. Remember that life is to be enjoyed. Most of us have no desire to work full time (self employed or otherwise) after retirement. By adjusting your life so that you NEED less, you will come ahead either way.
When I chose to stay in my home, keep the cable, travel and quilt, I accepted the fact that extra money would be required beyond social security and pension. However, that was a conscious choice., as was the one to commit to working for myself (at least for now). In my case, I need the ability to work around my school schedule. I like and need to be at home, much of the time. At another time (post degree) I may choose the employment option, or I may freelance as a translator, who knows. Everyone makes different choices.
My last thought is this........when it comes to employment or self employment those of you who are couples should throw out those gender roles already. I say this as a woman who spent most of her life as an at home mom and wife, working here and there to bring in a bit as it was needed. If the primary breadwinner wants or needs to not work, perhaps the other partner should take a turn.