I am interested in learning what the average costs are associated with
developing, hosting and maintaining an online social networking
community site/platform (typical to a myspace, facebook, etc but at a
start-up phase).  What vendors are out there that specifically
focus on community sites?  How much do they charge?

Hi! Thanks for the question.

I am listing here a set of services and platforms that can start a
customized social networking service for you. Please take note prices
vary from a few dollars to thousands of dollars depending on the level
of service. Whenever possible, I also included the price or links to
cost details in case they have various pricing mechanisms.

Sparta 
http://www.spartasocialnetworks.com/pricing.php

Siteground - $4.95 per month
http://www.siteground.com/index.htm?CB=1&hop=jsjohnson 

E-Friends - Software only ($280)
http://www.alstrasoft.com/efriends.htm#2 

Web Biz Ideas - $1999 to $2999
http://www.webbizideas.com/community/community.htm 

DZOIC - $100 to $349 (Software only)
http://www.dzoic.com/order.php

Build A Community - $199 and add $75 for hosting
http://buildacommunity.com/instantcommunity/index.html

Multicity - No price information
http://www.multicity.com/solutions/index.html 

iCohere - No price information
No price information

Bryght - $39.95
http://www.bryght.com/node?from=35

vConnect - Video Social Networking for only $30 per year
http://www.vsocial.com/vconnect/

SNAPP - $99/month
http://www.me.com/_snapp/


Searched terms used:
start create your own "social network" community
software hosting

I hope this would help you in your research. Before rating this
answer, please ask for a clarification if you have a question or if
you would need further information.
                                                          
                              
Regards,                              
Easterangel-ga                              
Google Answers Researcher

Thanks for the work!

Hi,

During a software development project life cycle, following costs are associated

Web Hosting
Security (SSL certificates)
Payment Gateways
Search Engine Marketing
Graphic Designing 
Software Licensing 
Project Development (Coding)
Project Maintenance
Marketing

Different companies charge differently based on their hourly rates?

Hourly rates vary depending on the technology of work, how urgent work
is required and company past experience?

In my experiences such website can be developed for 8 to 10 USD per hour rate.
Such project can take about 5 to 6 months (implementation time) if a
team of 5 work on it.

Though I am not directly related but currently I am working for www
dot savefinder dot com as an onshore technical consultant and they
have followed almost the same number of steps (10 months before). They
are being supported by some asian technology company to help them. I
am not mentioning its name since I am not marketing them here...

Hope this helps!
Personal Shopper