patty cakes Home Depot sells a junction box designed for ceiling fans. It has a metal L bracket that is riveted into thew top of the box and has 4 to 5 holes to screw the box to the side of the ceiling joists. The L bracket also has spikes that dig into the wood to provide extra strength. I would recommend using these boxes for ceiling fans or moderately heavy fixtures. Most fans weigh close to or more than 25 pounds. However, when they spin they put a lot more stress on the box holding it than the dead weight of the fixture. Regular j boxes for light weight ceiling fixtures have 2 nails holding them into the side of the joists - and these nails stick into the joist by maybe 1 inch or so. It is dangerous to hang a heavy fixture - or fan - on one of these boxes with just 2 nails holding them in place.. For heavy ceiling fixtures, they also make a special box that has 2 bolts the attach from the bottom of the box up into the joists. This type of box should be used for fixtures that weigh up to 80 pounds. They make other boxes with brackets that bolt between joists four very heavy chandeliers that weigh more than 80 pounds if you have any of these. iIt is true that electricians will typically install standard j boxes unless you spec otherwise. I would make sure that your electrician uses the proper rated box for the weight loads you are planning. The special boxes are inexpensive and worth the peace of mind that the fixtures won't fall out of the ceiling.

Where is the junction box relative to the vanity/sink/mirror. Depending on the location you might want to consider swagging two small globes or similar. The best solution is to have an electrician install the correct wiring and box for something like a flush mount and/or sconces. I'm concerned about a low hanging chandelier hanging directly over where you would walk. Open bulbs could be easily damaged. How far off the floor would the bottom of this fixture be.

RenoRooki, it seems that you have it pretty figured out. You're right about finding a joist to hang the chandelier from. There must be a reason the box is where it is. If you're going to find a joist to hang the chandelier from any junction box will do, but if you're using the box make sure its correctly rated to avoid having to re-do the ceiling AND get a new chandelier. Then you may have to move it anyways. Colby has a video explaining the process of hanging chandeliers. I hope it helps! Here is a link that might be useful: Del Mar Fans & Lighting-How to Hang a Chandelier

The best thing would be to buy based on price (which will likely be at a big box store), and install them yourself or get a knowledgeable friend to help. I've never had a problem returning the occasional defective product to a big box store. Switching out light fixtures is one of the most basic DIY projects you can do and it's pretty easy to quickly read up on how to do it, or get a friend to help. I'm no electrician, but I taught myself enough over the years to know what I'm doing, and I've helped quite a few incompetent friends do this. Turn off the breaker(s) supplying the power, take down the old fixture, and mark the wires; then hook the wires up the same way for the new fixture, and attach it to the box. It always pains me to see someone buy fixtures and then spend more on an electrician to install them than the fixtures cost. Resolve to teach yourself this basic skill, and have an experienced friend available who can help if you are unsure.