Longer than most expect. Beyond the initial process there are two years of conditional permanent residence and a further petition ordinarily filed in the ninety days before the second anniversary of conditional admission.
Plan for the filing that comes two years later
The question worth asking at the beginning is what the household's life will look like at the point the removal of conditions falls due, because the evidence for that filing is generated in the intervening period. The capital has to remain invested, the enterprise has to operate, and the jobs have to be created and documented. Households that treat the initial approval as the conclusion often reach the second filing without a file.
Ask now who will keep the records, how often the position will be reviewed, and what the plan is if the enterprise's performance diverges from the projections. It is also worth asking what the household's exit would look like at each stage, since knowing the cost of stopping is part of deciding to start.