This is a very difficult question to answer, but in a nutshell, firms can take as little as two to three weeks to agree a sale, and as long as three or four years, if not longer than that.
There are a whole host of reasons for this, and achieving a sale depends on a huge amount of factors, including luck, circumstances, the economic climate, your geographical location, your profit margins, the number of staff, the types of law, the structure of the business, the property used or owned by the business, your website, plus many random things you would never think of (and neither would anyone else other than the buyer!).
Timing and luck
Selling a firm is very often a question of coincidence – coincidence that a buyer just happens to be looking specifically in an area, and you happen to be looking to sell specifically in that area. Although of course there are lots of things you can do to improve your chances of success, the answer to the question how long does it take, is just that it really depends on the circumstances of your firm.
One thing that influences sales dramatically of course is the expectation on price a seller may have. Sellers with unrealistic expectations for the business they have for sale tend to find it considerably harder to sell quickly, if at all, and often sellers who have very unrealistic expectations will either never sell or take a very long time to sell, usually up to the point when they decide to drop their expectations down and be more realistic in the price they are expecting.
Law firms remain fresh
It does not really matter to a certain extent how long it takes to sell when it comes to a price – the sale price of a law firm will not depend on how long it has been on the market for in the same way that a house sale does. Firm sales do not become stale, so it does not really matter if you decide to put your firm up for sale but then do not sell for a couple of years. Every buyer coming into the business will be in the same position as looking at it from afresh.