Don't pay attention and don't do any free/test work for them. A lot of ppl can be scammers and take advantage. So unless they started the contract and put the price on the escrow protection don't start the work!
After a month or so of non-communication from a client I close the project. Having idle contracts appear to be active can prevent some potential clients from contacting me, thinking I am too busy to work on their projects.
And if a client is no longer interested in his/her project, why should I be?
After closing a project I message the client telling them that a) I enjoyed working with them (whether or not that was true) and b) we can re-start at any time at the client's convenience (whether or not that is true).