Bear in mind I haven't a clue what you have in mind so some of this may be irrelevant. I have gone down the tortuous route of producing a product my self though so I have some experience of this.
Patenting:
For a product to be patented it must be unique, i.e. there is nothing out there that does the same thing; or if there is, your new product accomplishes this in a different way. To my knowledge, there are tax exemptions for profits derived from a patented product. I don't know if these exemptions are applicable to company profits, or the inventors income from the company. A good accountant could tell you that. To see if it has already been patented (just because this product is not on the market does not mean it has already been patented) you need to search patent databases.
http://www.uspto.gov/patft/ is the US patent database web address.
http://www.patentsoffice.ie is Irish one.
Patents may be confined to one country, several countries, or worldwide. (cost increases with territory).
Most patents have finite life, eg 10 years, after this anyone else can copy your design.
I'd say it's a long tortuous process to be honest. Try the searching yourself, it's easy enough, and it'll save you a chunk in patent attorney fees. But if in doubt get good advice.
Manufacturing:
Obviously you need to decide what costs are involved in producing the product and what you can sell it for. And remember if you sell to a shop the price you receive will be well below the retail price, when the shops margin and VAT are taken into account. alternatively you could sell direct to customers on the web but this means you've to spend a bit on advertising.
Also, the product may be simple enough but it may need to be safety approved before you could sell it on the market, e.g. CE mark (conformite europeene). Not all products require this though.
This reply is taking way too long and not sure how relevant it is so i'll cut it short. best of luck.
Ger