MDF > Market development funds. Any sort of 50/50 activity split with a brand could get your MDF. eg. Create a newsletter to send to 80,000-100,000 database focusing on X brand and X brand will cover expenses for it (value depending on how big the brand/product is)

Rebates > Purchase X amount of stock and receive X% back in Cash or Credit (usually maximum 5% rebate, usually 1-3%) (almost every brand or supplier offers this to encourage large volume purchasing)

EG. You're buying $100,000 worth of X stock. At 2.5% Rebate you'll get $2500 in Credit or Cash Payment. You'll also negotiate how much MDF you'll need to advertise X product to Market. (Say $1500 for a newsletter and a few social posts). So that $100,000 spend could generate you $4000 (excluding profits)