It sounds like you are talking about what is called "designer inspired" or brand inspired. For example, a phone that looks almost identical to an Apple iPhone, but it has no iPhone branding.
So long as you are not infringing on any copyright, trademark issues, there is usually no problems at all. Now in most cases these type of rights are tied up in the name or logo, however that's not always the case.
Some companies may have a licence on a design aspect of a product or even on a symbol that they use on a product. This is where it can get a little messy, so knowing what the protected areas of any product are is critical to staying and arms length away from any potential drama.
I think you'll find as time goes by more and more companies will be trying to licence as many aspects of their product as they possibly can, in an effort to reduce the unbranded clone market.
I'm not trying to put you off these types of products, far from it as many do deal in these types of products, and because of the price difference, can do very well with them.
Just know the products you are selling, know them inside out, that's the very first thing would be my advice. Once you know what your legal obligations are in distribution, then you know exactly what you need to look for from a supplier.