You've looked at your finances, your ideals for a happy retirement, and the research, and you've decided to start working for yourself come 65. You have a plan for your business and a passion for learning that will get you started.

Here are the other critical factors you need to take into consideration.

Risk and affordability 
Starting a business of any size or shape is never a simple matter, but with the right guardrails and support network in place, you can make it a success. That said, now might not be the time to jump into a capital-intensive business venture unless you can comfortably afford it.

Affordability, of course, doesn't just mean money: It also means time. Investing in a new restaurant or widget factory might sound like the culmination of an outstanding career, but it can be taxing on even a seasoned young professional. 

So consider realistically what you have the time, energy, and means to start. If it's a consulting business based from your home office, you probably needn't worry. The flexibility of freelancing or consulting can ease you through any growing pains without costing a lot of retirement money to get started. 

If you're looking to start something more costly and you have the experience, money, and/or energy, go for it -- just be sure to get some support. That might be practical (an assistant) or emotional (a trusted advisor). 

Whatever the case, think ahead about what you have the time, energy, and investment capital for, and how that matches with what you want to do. From there, you can adapt your strategy or make a contingency plan if things don't go according to plan. 

Household space 
Working from home isn't as simple as hanging up a shingle. 

First of all, there's the matter of the dreaded cabin fever, not to mention the practical difficulties of living and working in the same space. Will your laptop be shooting you angry looks while you catch up on the game? Will your papers get lost in the shuffle of household documents floating around?

With the benefit of experience, consider what you'll need to make your workspace, well, workable. Many find that a dedicated work area solves many of these problems -- it could be a good time to move around some furniture in the guest room or turn that little open corner into something functional.  

If you have a spouse, this would also be a good time to consult with him or her about what would be best -- and most tolerated. Some people don't care if you spread your projects out all over the living room, while others might not be so enthusiastic. 

Your health 
Whether you want to dabble in some small projects or take over the world, the fact is that your health is a relevant variable in the business decision. Don't get me wrong; it always has been -- it's just that younger people are typically too myopic to realize it. 

On a day-to-day basis, do you have the energy and the strength to undertake what you want to do? If you're not sure, consider finding ways to minimize the effort. Maybe a virtual assistant could help, or a rescaling of objectives. 

On that note, look after your health: As an entrepreneur, you're in the rarefied company of people who want to and are able to execute on controlling their own destiny. Extend that powerful thinking to your life and eat well, get rest, and exercise. You'll be a better businessperson for it, and it'll help you enjoy the experience of entrepreneurship all the more. 

There are also, unfortunately, unexpected health risks to consider. While a major health crisis might not throw a wrench in things the way it might have when you were a young parent, it can still do a number on your plans. 

Therefore, make sure to have a plan in place. That includes health insurance coverage, some padding in place to meet business or personal expenses should you get derailed, and a contingency plan to keep the business running (if applicable). 

Address these three major areas, and you are well on your way to an entrepreneurial retirement!