uspto.gov says "It (a provisional patent)can be filed up to 12 months following the date of first sale, offer for sale, public use, or publication of the invention, whichever occurs first." But I have always heard that if you sell your invention without a patent or post about it online, it immediately becomes part of the public domain, and hence I lose patent rights. Hopefully someone can clear up my confusion?
The answer is yes, but it always depends. Let me begin by saying that the more knowhow, etc. involved, the easier it is to sell something without any patent protection. Otherwise, you are trying to sell something without protection and you get no protection until the patent issues, which may take years.
The acquirer may just run with it (I would) without licensing knowing there is no cost until your patent issues. Then, when you file, they will see your claims and try to modify their product around your claims. It is slightly vicious in nature. That said, I may not act much different if you file first, unless I can buy your patent or the license costs are very inexpensive.
Secondly, many countries have absolute novelty and you will not be able to protect your invention there ever, even if a licensee arises and wants to enter those markets. This too, is a serious limitation for licensing.
My conclusion would be that you are underfunded to address your IP and that I can get away with murder. Filing the application is your way of telling people that you are serious. That said, it is not necessary and I have a lot of clients that file later or never file.