There will always be people who claim they can build a community in a matter of weeks.
One author published a book claiming she could do it in 25 days. Yet, even the author's own community hasn't had activity in a month. Note: this community has been closed since the time of writing.
We've lost a LOT of potential clients by being honest about how long a community will take and trying to set realistic expectations. Usually they go with a marketing agency instead which promises instant results. Every time, they've been disappointed.
There aren't any easy short-cuts here and you should beware any group/individual which claim you will have a thriving community in a matter of weeks. It take both far more time, and far more effort, to establish a community.
Bonus: Download your free copy of The Proven Path. This eBook will explain, step by step, the only proven strategy to developing a successful online community.