In my opinion, there are two possibilities. If development is something you’re good at or passionate about then sure, go ahead. If not however, then you’re better off letting those who are do it for you. At the end of the day, it’s all a matter of crunching some numbers.
For example, a 500-word article costs 10 bucks over at MegaSites.com (my development service, I blogged about it a few days ago). Would you be better off writing articles yourself?
Most likely not.
As a person who doesn’t write articles for a living, it might take you let’s say one hour and 30 minutes to write a 500-word article (people who write articles for a living are obviously able to do it faster and in most cases better). In other words, you’d invest 90 minutes of your time writing that article instead of paying someone 10 bucks to do it, essentially earning a little over $6.5/hour (you’d earn 10 bucks for 90 minutes or in other words, a little over 6.5 dollars per hour).
If $6.5/hour is more than you make through your current occupation (domaining, your day job if you have one or anything else) then sure, go for it. If however you currently earn more than $6.5 per hour, you’re better off letting someone else write the articles.
Capital/time allocation 101
The same principle is valid when it comes to design.
Perhaps in your case, the numbers are different. Maybe it takes you less than 90 minutes to write an article, maybe it takes you more but I’m sure you get the point.
Again, if you want to treat development as a hobby or if you’re good at it then yes, developing domains yourself make sense. If however you want to be pragmatic and maximize revenue, let someone else develop them.
A lot of you guys make considerably more than $6.5 per hour, so building websites yourself just doesn’t make sense. Some domainers are used to operating as a “one man show” but it you truly want to maximize revenue, you have to start letting other people take care of the tasks it’s not economically rational to handle yourself.