Answer: You could try to start with samples, in some cases you can get them for free or at a low price from hair wholesalers. Use these samples and a color-ring to show your potential clients the products you are selling and only buy the extensions after your clients paid you first. With the money you received you can purchase the hair from a supplier. In most cases you need to buy a minimum quantity to get wholesale prices (cheaper) so you should try to get more clients interested in your hair and place your order at the supplier at once.
Next to this you can also join affiliates programs, in this case you refer clients to another hair extensions seller, but you will receive a commission for the referral. It will not be the experience of having your own shop, but you can grow into the business, develop your marketing skills and earn money at the same time. With this money you can start to buy your own stock of hair extensions.
There are wholesale companies that work with distributors; they will support you on marketing and the products, so you can focus on the sales.
Some countries offer special grants for people who want to start their own business, you need to submit a solid business plan, but this you will need anyhow if you want to start a business.