You'll have to set a sales goal or tipping point, which is the minimum you need to sell in order to have your shirts printed. Then ... you can sell your own T-shirt designs, stickers, tote bags, ...
From bedding and tote bags ... bacteria to a minimum. If the collar is made from fabric, it might be machine-washable; check with the care label to confirm. If it’s good to go in the washing machine, ...