There is a choice that every would-be dreadhead has to make - are they going to get a professional start their dreads, or are they going to do it themselves? Arguments can be made for both sides as there are pros and cons to both options.
The most popular dreadlocking methods - backcomb and twist & rip are both relatively simple, it only takes an evening of watching youtube demonstrations and before you know it you'll be able to make dreadlocks. This makes it possible for pretty much anyone to make dreadlocks on anyone and paves the way for the homemade dreadlocks!
The most obvious benefit to DIY dreads is that it's quite a lot less expensive than those made by a professional. It'll only set you back the cost of a friend or two's weekend.... which is roughly the price of a couple of take out pizzas! and maybe a little extra for a backcomb brush - not exactly break-the-bank sums.
With DIY dreadlocks you also have complete control - you choose the methods, whether any products are used, whether any tools are used and how long you work on it at a time. You're also learning a new skill that you can help you if you need to redo your dreadlocks - or create them on friends!
DIY dreadlocks can also be considered more personal as you and your friends created them and you will always have the memory of the time spent making them intertwined with the dreads.
The downsides of DIY dreads is that while the starting methods are relatively simple, there is still a skill to it. The dreadlocks you make first won't look as good as the last ones you make - you'll have learned and improved your technique - not everyone is that happy to be the guinea pig for their friends to learn how to dreadlock on.
This leads me onto salon/professional dreadlocks. A dreadlock professional is someone who has created dreadlocks before, they've got the skills, the technique and the knowledge. They'll be able to create consistent dreadlocks without the trial and error and also have advice on care and maintenance. They may also be able to help you if you need any physical maintenance in the future.
The downsides to pro dreads are: well the big one is the cost. Dreadlocks can take a full day of work to create and that time is not cheap as it's intensive work. The costs will vary depending on who's doing the work but it's a lot more than DIY lets put it that way.
Salons also often get a bad reputation because many will often heavily promote wax use. When you pay a lot of money for dreadlocks.... some people expect them to be instant and when it turns out that dreadlocks actually take months of patience regardless of the starting method.. well then some people might go and complain to the salon that they're not happy with how their young dreadlocks look! So many salons will use wax to help avoid this resulting in more "together" dreadlocks at the start but often leading to negative effects further down the line. - I do not recommend wax use.
My advice is to fully research whoever is going to make your dreads - check out their website if they have one or facebook page, check out the methods they're going to use, whether they use tools or products and make sure you know exactly what they're going to do to your hair and only proceed if you're 100% happy with what they're going to do.
An important thing to remember is that all this is about STARTING the dreadlocks! Either way they're still going to require months of patience and after they've matured it'll be very difficult to tell whether you or a pro started them (depending on the method and techniques used) so it really comes down to how you want them started.