We have had similar occurance at our church, a member wanted to start a ministry to the homeless and forgotten people in our area, but instead of creating the ministry under the tent of our church to get underguirding and support, he kind of insulted the system went to solicit support from various churches and never really got it off the ground. He did not want input from any church, but wanted their support for this ministry. I met with him and gave many ideas for how it could work through our missions support from the church, let’s begin and see how it unfolds. It is a great need for our area, he lasted about a month with just an idea, but lacked the drive to see it through.
Support of a local church is vital for missions to begin. Find God’s calling on your life, let the local body support you financially and prayerfully, then run with it.

Certainly there’s nowhere in scripture that mandates membership in a local church.  In fact, I wonder if the NT writers even considered the distinction that would one day be drawn between “local church” and “universal church”.  As Ray noted, Paul and Barney were sent by the Antioch church and seem to have remained connected and accountable to that body, even as they traveled throughout the region planting new churches.  Here are two principles I think can be safely drawn from scripture:<ul>
<li>we are to continually, regularly meet together as a body of believers (He 10:24-25)
<li>we need to be accountable to that body (Ac 13-14)</ul>
I think it may be safe to say that the only legitimate exceptions to these principles would be for those whose work is pioneer church planting; i.e., planting a new church where no church currently exists.  In that situation, I think it is important to be sent by and accountable to a particular church (as Antioch was for P&B;), but it is just as important to be connected with a body of believers (if one exists) in the area where one is seeking to plant a church.

If you live in an area where there is an existing church (let’s say, oh, just about anywhere in the western world), then I think it is vital to be connected, committed, and accountable to a local body of believers that we know of as “a church”.  I am going to conclude with that statement, recognizing that it leaves the door wide open for discussion about what constitutes “a church”.  (E.g., Does it need to be formally organized? Does there need to be someone or some group providing some level of formal leadership, whether that is a pastor(s), elder(s), etc.?  Is there some minimum size needed?  What about membership?  Probably we don’t need to take this discussion down those roads here and now, but they should be considered in trying to answer the question of whether commitment to a particular church is biblically necessary.)