Hi and welcome to SaleHoo, Vassilij! It's great to have you here.
That's true, before you can access a supplier’s wholesale prices and place an order, you usually need to go through an application process and be approved as one of their resellers. Not all suppliers are this formal, but most have at least a couple of requirements you need to meet before they will work with you. One of the reasons I can think of - wholesalers need good customers – they aren’t too keen to sell 5-6 items to a new eBay seller for example, who may or may not return, they also want to be sure that the retailer is going to sell their product effectively.
Occasionally you may run into suppliers who want to see a business license before they will sell to you. These suppliers will generally have large minimum orders and wish to determine that you are serious about purchasing their goods. Some suppliers will ask for a sales tax ID. Usually you just need to provide something equivalent in your country, for example your VAT registration in the Philippines.
One other thing I'd like to point out is the type of product you're interested in. It's actually one of the most competitive markets online. You'll find that most electronics products like mobile phones sell at the wholesale price or below wholesale on eBay. That's just how intense the competition is. If you really want to sell mobile phones, you're going to have to purchase in bulk quantities to drive the wholesale price down or buy liquidation.
We do have mobile phones suppliers in the directory and if you search the forum by "phones", you'll find a handful of related posts like this -
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And yes, you'll need to contact the suppliers directly to get wholesale prices as most of the time, the price listed on the suppliers' site is retail, but it's still going to be cheapest overall if you source the products straight from the manufacturers.