The marketing effort for 300 N. Michigan Ave., a planned mixed-use development in Downtown Chicago, has started during increasingly tough times for new residential properties, though predicting market conditions throughout the planned development period — more than three years — is difficult. Plans by developer Provence Development Group call for completion of the project in the third quarter of 2011.According to a recent report by Appraisal Research Counselors Ltd., a record number of condo residential units will come on line in Chicago in 2008 — all of which began construction before the credit crisis made funding for such development more difficult. The report estimates that about 5,900 new units, including both condos and townhomes, will be put on the market in 2008, compared with about 4,300 units in 2007. Most of the new units in 2008 will be in the Downtown market.Plans for 300 North Michigan Avenue call for about 28,900 square feet of retail space on the first two floors, a 300-room hotel on the third through 23rd floors, a 225-unit multifamily component on floors 24 through 52, and a 160-space underground parking garage.According to the Chicago office of Holliday Fenoglio Fowler L.P., which is undertaking the marketing effort, investors have the option of buying the entire development or individual components, and would then have input in the project’s master plan, as well as being able to complete the interior architecture of each component to their own specifications. The development is being marketed without an asking price.A spokesman for Holliday Fenoglio declined to comment about the project when contacted this morning by CPN.