When you are trying to sell yourself, even for a measly $5, a lack of attention to detail isn’t going to do you any favours. Everyone makes mistakes, especially while typing. So often we publish things without double checking them for spelling, grammar and accuracy.
Typos in advertisements though? Not really acceptable when you are claiming to be “proffesional”. Even if the fee is just $5, would you want to buy a piece of creative work from someone who makes such a blatant error twice in their advert? Would you trust someone to help you “BEEN SEEN” on the net? Even if they only wanted $10 for the service?
You might fail to spot mistakes in articles but when you are writing an advert of around 25 words to ask people to pay you for your skills, surely accuracy is vital. If people are judging you on those 25-or-so words, a lack of accuracy is going to make them think less of you. Even those who are writing in a second or third language have tools at their disposal to check spelling and grammar and, of course, social networks full of friends to ask.