If you are thinking about starting a new business, it is best that you do it before you officially retire. There is a couple of benefits of doing so which I shall cover below.
When you hold down a job, it is easier to secure financing for your new business. Whether is it a business loan or going to direct lenders for payday loans, you will get approval if you supply the documentations needed when you have a job. When you are retired, it is much tougher to secure any kind of financing, especially from banks.
When you are still active in the job market, you will meet more people relative to when you are officially retired. You can take this chance to do some networking for your new business. Talk to people and see who are potential sales leads or business partners. It is difficult to get a meeting when you are not on a official business so take the opportunity when you still have a job to secure as many meetings as you can.
A new business carries a lot of uncertainties. Certain assumption you hold might not be true, which can derail your business. As a result, if you new business doesn't generate cash straight away, and you are burning away your hard earned savings, it can pretty stressful if you don't have your job as another income source. Doing a new business is already a stressful event and you want to avoid adding to it by having cash flow issues as well.
The downside of holding down a job when starting a new business is the additional hours you need to put it. However, I think the benefits outweighs the cost of doing so.