Working with a landscape designer - Advice?

After staring at our small backyard with the dead lawn for a year now (sad but true!), my husband and are I thinking about hiring a landscape designer to help us get it together! This is because we think we'll need some hardscaping as well as help with plant selection. We don't have unlimited funds however, and I'm a little nervous that either no one will want to work on a limited budget OR they'll end up getting us in over our heads! Has anyone out there worked with a landscape designer before and have any tips for how to make sure a project doesn't get out of control? Much appreciated!!