The Google search engine excels because it responds and ranks those websites and blogs with activity. The original term used at Google was "back rub" - similar to a pat on the back by a good friend. It is a way to recognize achievement so the results are more focused. The back rub is ranked by the number of visitors and page duration.
To take your online presence to a new level, the best method is multiple "back links" and focusing on an unique niche market.
In my opinion, there is no finer site than HubPages but putting all your eggs in one basket 1.) doesn't increase your online presence, 2.) doesn't increase your search engine tags and 3.) limits your learning experience to only one site.
Having your own site is best but only if that site is promoted. HubPages is the best place to begin and the best place to complement your other writing sites. However, IF your author score falls below 75, essentially your work on HubPages is not seen by the search engines. Keeping your author score up is critical.
So having stated all of that, the best time to start your own blog is when you can generate traffic to your own site.
My specific question really is how do I know? I am fearing failure at developing my own site. The stats here are very clear to monitor. How do I know IF and/or when I am failing at my Wordpress site?
Are there mile markers on WordPress to guide you when you should move to a self hosted site?
Should I spend the money on the self hosted site IF I am only do this part-time and my writing is just generating a nominal amount of money?
There is no question IF you are a full time writer, both HubPages and your own self hosted site are profitable.
The question is how do I determine the timeframe to wait? I don't wish to self host if there is insufficient return.