Simple economics makes it unlikely that you will be able to sell yard trees. Loggers are in the timber business and there must be value with enough timber volume to offset the considerable costs of bringing heavy equipment, cutting and hauling the logs, paying you for the trees, and still being able to make a profit. Yard trees are more difficult to harvest, typically are of lower quality than woods-grown, and may contain embedded metal which can damage saw blades and other timber processing equipment. In rare cases it might be possible to market the sawlog portion of high value trees, such as black walnut, to local woodworkers or portable sawmill operators. However, finding a willing buyer would require a significant effort on your part. Yard trees can have more value as part of a well maintained landscaped property. If you want a yard tree removed, you should get estimates from several certified tree service companies. Some companies may be able to sell your larger trees but they would not be able to cut your trees for free or pay you for your trees, but this can offset their costs and affect the estimate you receive for their removal.
A minimum of 10-20 acres is typically needed to contract a logging company to harvest your timber. Modern, efficient logging operations require high capital investments in equipment and harvesting low volumes on small acreages is usually not financially feasible. The cost of moving logging equipment from one tract to another is a major expense for loggers. So larger tracts will receive higher prices per unit of volume sold, especially if they are located near quality roads. The threshold for financial viability is also affected by the volume per acre, tree size and quality (grade).