- Not charging the right price per hour, because "I was starting, this was an opportunity". - Not putting boundaries on client limits, as in, "no you can't call me whenever you want" (especially if you live in a different timezone) I personally understand they need to have an answer, but they can do perfectly fine by e-mail and you'll have to set to them a deadline for replies, for example "I will call/or reply you as soon as I get the e-mail" on the contract. - I didn't bill them for every cost they make me do like travel meetings and other general costs, so at the end my profits were even low. - I didn't had a contract, that was completely solid, so, get a lawyer who can draft you a solid contract with all your needs. - I was so overswamp of work that I couldn't manage all the expenses, or other time that I didn't bill to them, so also, get an accountant if you are charging them with something that might be funky.