When I worked for the local press, and for national magazines, it always better to do more than a 'one off',( you should also recieve a discount for a booking of 6 adverts) . Reasons for more than a one off are :-
Nobody reacts to a single one off advert, people have to see it 2 or 3 times before they'll make a decision, then when they do they look for your advert, if your not there then your opposition may get the call.
People expect to see you in certain places like the local paper or yellow pages(I was regional sales rep of the year for yellow pages). If they have been recommended to use you they need to be able to find you, there's a new classification called 'Nail Technicians' now too. I'm in my local one. It's cost me £116 + vat for a small 1.5cm high box acorss one column and you can pay by 10 monthly installments. Got be worth that - 1 new regular client will pay that off in no time!
Please feel free to ask me about any type of advert, i'd be happy to do layouts for you etc if you like.
HTH XX