What legal issues I will face if I manufacture and brand a product similar to one that has a patent?
If you infringe a patent then if the patent owner or an exclusive licensee take action against you then you are effectively earning money for them as they can get damages against you and get all of your profits and more. They can also prevent you from continuing with injunctions.
Patents are powerful legal instruments. If you ignore them, you could end up seriously regretting it! You need to check if you are infringing a local patent in your jurisdiction and in the jurisdictions where you source your products from.
Get a patent attorney to do a freedom to operate (FTO) search before entering the market with your product.