One of the big issues with this is the fact that even if everyone on this forum who is currently active bought something, you would be hard pushed to see a return on your investment. As Trey has said, there is a huge number of suppliers out there and potential customers. Getting your products/services to the potential customers is not easy in a flooded market.
One rule of thumb I have always found to be fairly accurate is that a new business will not make a profit in the first year, you have to be able to sustain yourself and family (if relevant) for that period while any money coming in goes back into advertising and materials.
Setting a retail price for your service or goods is also very tricky. We often look at some of the bespoke or off the shelf modifications/accessories for kits and think they are expensive. I reality, the profit margin on them is very small given that there is not mass sales for every manufacturer even if there are mass customers, there are just so many at it.
You have to come up with the ideas of making a potential customer come to you rather than anyone else. Also you have to consider mass producing some parts and offering them up to retailers at a wholesale, and maybe even 30 credit terms. Initially you may consider doing this on a sale or return business so that a retailer could try out your products without risk of being stuck for stock. They know their market and they will not take risks in this day and age.
Foe one offs or mass produced the costings are very important. You have to source your materials and equipment down the the slimmest penny as you have to factor all of this, including things like business insurance, banking charges post and packing and your time. Whenever a customer hands over money for something, they have to be contributing to these costs not you. You also have to live so your customers have to pay to keep you in your ideal lifestyle. getting the costings right as a manufacturer is not easy at all.
If you are losing your job through redundancy (I am sure that there will be a few that do before these dark days in the UK are over, myself included) then you may be able to get help and advice on starting up a new business from your local agencies. Ask at your Citizens Advice, Jobcentre or other such places. Depending on your age, you may also be able to look at a grant. At least they will be able to offer advice on creating a business plan which is essential if you are going to deal with banks and insurance.
Don't think that this all sounds over the top, it isn't. Setting up a business is a big deal and you need to get it right, there are plenty of people out there who's job it is to advise you and, initially a lot of this advice is free. Also don't think I am trying to talk you out of it, I certainly am not, in fact I wish you the best for your enterprise but get your thinking cap on now. Do your research, check out suppliers, work out costings but above all, be realistic. Something like this may mean that to get it off the ground yo have to work for 'the man' part time to live on while the rst of the time you work on your products, it will not happen over night.
I do wish you good luck with it though.
