If you decide on hiring a link builder with a low service fee, then make sure that to know all the strategies, tactics or methods that they will employ to increase the rankings of a client's site. The last thing you want is to have an angry client complaining that the cheap SEO you hired has damaged the site's rankings or incurred penalties due to manipulative tactics.
A cheap link builder can be useful if one does not have a lot of time to execute a plan to get high quality links. It would be better to create a solid plan to increase your client's ranking using great content, natural linking methods, and building an online brand. Then perhaps one can hire cheap help if you need an extra pair of hands to put the plan into action. Keep tabs on the affordable SEO you hire to ensure that he or she sticks to the plan and does not use any short cuts to earn quality links for your client's site.