A ten year tenant is naturally going to feel territorial. In this case, its parking thats causing the issue. However, you have a TEN year tenant. Stephen(WA) is correct in asking you if this is a tenant you want to keep and if so, speak with him about the need for raising the rent. Your state may have an annual cap on how much you can raise the rent - check that first. The tenant CANT refuse the new terms - he can either accept them or leave.