If you need a website like facebook , first of all the website can never be developed in 10000$ , Minimum it needs 50000$ to develop a social network and regarding price i just gave you estimate. First I need to know what exactly you need (i.e, credentials).
Regarding CMS also I don't work with jhoomla. I have my own CMS. The reason why my CMS its best because its fully customized and enable quick page loads.I have developed more than 100 projects in my CMS.
Regarding myself :I have 12 years of experience in all fields of web-development, so I can provide you complete integrity of service.
I can develop anything from the scratch without any framework. Moreover, I have developed my own framework, it shows my high skills.
We are talking about a portal, it means - big, high load project with good structure and caching system , if structure and caching is not done in proper/appropriate manner , the entire website will work slowly or even will be down at all which will feel irritating..
I know how to make your portal efficient and convenient for both sides: for you as an administrator and for your visitors. I have experience in developing big portals.
I know how important is to have reliable developer who not just develop the website and leave but who will provide support and all needed updates during whole life process of the portal. You can rely on me and you'll get the best product you could expected.