Homes built with basements have some risks that other types of homes don't have. One of these is water leaks. These are problematic because they can signal very serious problems. In some cases, you won't know that there are any issues until you start to see puddles on the floor. If the basement is finished, this can cause damage.
Construction problems are to be expected in many cases. Reputable and experienced contractors will plan for these issues. It is imperative that anyone who is going to have a project done finds out what kinds of delays, if any, the contractor has planned for. Even if this isn't discussed in the contract, you can ask about it when you are discussing the project's specifications and terms.