I'm looking to file bankruptcy how long should it take from start to finish? And how to find the cheapest lawyer.

The time a bankruptcy takes depends upon which chapter a person files under. A chapter 13 plan lasts between 3 and 5 years and for people that are over median income level for their family size must propose a 5 year plan. A chapter 7 is normally concluded in approximately 4 months, but can be completed in just over 3 months and sometimes takes much longer if complications arise.
One of the best ways to find a bankruptcy attorney is to use the Avvo "Find a Lawyer" link at the top of this page and top of most of Avvo's pages, but remember looking for the cheapest lawyer may not be in your best interest. The phrase, "You get what you pay for" was coined for a reason. In the end, you may pay more because you found a cheap lawyer instead of finding an experienced bankruptcy attorney.