Yes of course, you can sell from products to services without an investment.
Products : you can select range of products click pictures , get data and start selling on various marketplaces like eBay, Amazon etc and once you get an order you can buy and ship it [ since you opt for prepayment from customer] so you actually get money before shipping of a physical product. Of Course its time consuming but with your skills and business acumenship you can shorten the time to grow the business.
Services : you can register yourself at Freelancer or such platforms and can provide any services [ which you are apt for] and you can start making money without investment.
Hope this brief helps you.