In this video, I go over how I personally made my own floating shelf that was strong enough to do pull ups on, and it was cheap! It cost me about $30 max for all the materials.

Tools:
Ryobi Miter Saw
Ryobi Nail Gun
Clamps
Hammer
Ruler
Level
Measuring Tape

Parts:
Lag Screws
Brad Nails
3 inch screws
1 inch screws
Wood Glue
Stain + Poly

Materials:
Cedar Fence Board - x2
2 x 4 x 8 Lumber - x2
1 x 4 x 12 Board - x2