Mark Ballas -- I Got a New Zip Code in My Step ... 90210

'DWTS' star Mark Ballas just dropped $2.5 mil on a fixer upper. It will make more sense when we tell you this ... the house is in a primo section of Bev Hills. It's a skosh over 4,600 feet, with 5 bed and 5 bath, but it needs major work.…