My best guess is that you'd get it close to wholesale price, which is anywhere between 30% and 50% off retail price in the electronics industry.

You'll need a sales tax license number to prove you're a business rather than an individual.

Pricing requirements will depend on the manufacturer. Some will have a "MAP Policy", which stands for Minimum Advertised Price, that dictates the price you advertise on your website. Note that "advertise" and "sell for" are not the same thing - that's why you see some sites that say "add to cart to see the price" - they're circumventing a MAP policy. Unless they make you sign a MAP Policy though, you should be free to advertise and sell at whatever price you want.

Margins can vary by manufacturer depending on whether they are first (eg. Samsung TV), second (eg. Toshiba TV), or third tier (eg. RCA TV).

In your negotiations with the manufacturer, I recommend that you discuss price protection to ensure that your margin rates remain neutral as the product becomes obsolete. Alternatively though, you may be able to negotiate lower costs if you choose not to be protected; however, you would want a robust exit strategy to ensure your margins are protected should your sales not materialize.

It depends on the Brand and Manufacture. If the Brand is desperate to liquidate the stock, then you can get bottom rock prices. You should do lot of analysis on the current selling price and your expected margin before negotiating the deal with the brand. Prices in electronics is always volatile. Even if you get a low price, you should have action plan to quickly clear the stock.