Section 21. If the income of the estate of a ward is insufficient to maintain him and his family or if it appears that it would be for his benefit that his real estate or any part thereof or any standing or growing wood thereon should be sold and the proceeds placed on interest or invested in a productive security, his guardian or conservator may sell such real estate or wood upon obtaining a license therefor and proceeding as hereinafter provided. If standing or growing wood is so sold, the guardian or conservator may grant to the purchaser the privilege of entering upon the land and cutting and carrying away such wood within such time as the guardian or conservator may allow.