Conflicts arise when a tree is on the property line. It may block light, leave debris or create a hazard for the neighbor. If the tree is adjacent to public property, maintenance tasks for utilities may put the tree at risk. Plan for the tree's mature size and locate it far enough from the property line to avoid confusion about its ownership. Maintain the tree appropriately. You may be held responsible for any damage to the neighboring property if negligence was the cause.
Generally, if a tree branch overhangs the property line, the neighbor probably has the right to remove limbs or roots on his side. Extensive pruning can impact the health of the tree. It's not permitted to interfere to the point that the tree's viability is threatened. But not everyone is skilled in determining how much pruning a tree can handle. Prevent adverse impacts on the tree by limiting the amount of overhang.
Trees are sized by the radius of the canopy. In small yards it can be difficult to retain the canopy spread within the property lines, especially with medium to large trees. Large trees take decades to reach full size, but depending on its rate of growth in 5 to 10 years will be substantially larger. It's best not to plant large trees near the house. But remember also the potential size of the canopy and overhang over the property line.
If a tree trunk grows to a size where it's crossing the property line it's still your tree. In years to come the ownership might not be clear anymore, and the tree is owned jointly. The decision to cut it has to be mutual. Ensure the long life of your tree by preventing future disputes. While there is no standard distance for planting trees, Surrey, British Columbia, advises planting large trees 6 to 10 feet from the property line.