For those starting out and looking to make wordpress sites for clients. Avoid free themes and 99% of the themes on the market. Look for the solid tried and tested multipurpose theme that have lots of good developer review. You might not like paying $60-70 but in the long run it’ll save you time and allow you to charge your clients more. Many free and premium themes are very locked in terms of style. If the client comes back and asks for the header layout to be changed or general style tweaks these can take hours and might require redoing beyond your abilities. But on a good premium multipurpose theme it’ll take just minutes. Also don’t cheat by look for free downloads. If its not for the proper site it could have all sorts of nasty stuff hidden in the code and will make you look extremely unprofessional.