Take it for a test ride before buying it to make sure you like it and that it fits.

Walmart bikes almost always need a thorough going over by a competent mechanic to make sure that everything was assemble properly. This is important for a number of reasons. Safety, first and foremost. Also because an improperly assembled and adjusted bike will experience rapid premature wear and damage. If you aren't knowledgeable/skilled, or have the tools, it's a good idea to budget a few extra dollars for a trip to a good bike shop before using the bike.

Good luck.