QA Selling Online

I found a product that costs $6 to $8 to manufacture and I can sell it from $27 to $30 but I don't have enough capital to supply the whole month. I have, let's say enough for 50 units when I need 300 to last the whole month. Should I just save up the money and then jump in or buy the 50 jump and then suffer the consequence or running out of stock?