Certified GKH Gardening Expert
Beans grown indoors can be sown at any time. Just make sure that you have enough light, and that your potting soil contains beneficial microbes. Plant them 3 times deeper than the width of the seed.
Growing beans indoors will require about 100 watts of light per plant, with 200 being around optimal.
If you intend to start them indoors, and move outdoors, then I would advise against this. They prefer to be started where they will finish.
For when to start- This can depend on the variety. Follow all packaging instructions on the back of the seed pack for information on when to start the specific cultivar. This article will help you to grow beans: