If I have 2 sons living in my second house without paying rent and with no signed lease, how can I get them out to sell house?

Technically, if a child is not paying rent, they are a guest and not a tenant. And a guest may only remain on the premises as long as the property owner allows them to. Additionally, that permission may be withdrawn for any reason at any time. If it is withdrawn and the guest does not leave, they becomes a trespasser and the police should help remove them. However, the police sometimes refuse to do this, feeling that the courts should determine whether the occupant can be made to leave.
d on the above, if your children claim a right to stay and the police will not remove them, then in order for you to do so, you would need to bring an "ejectment" action. This is basically an eviction for non-tenants. That having been said, if your children were suppossed to pay rent or a form of rent such as utilities, then even if they have not actually paid these amounts, they are your "tenants". In this case, they would need to be evicted. You could file an "unlawful detainer" action for nonpayment of rent or, in the alternative, as month-to-month tenants (on an oral lease) you may give them 30 days notice to vacate the premises. If they still refuse to leave, you would then need to file a formal eviction.
At this point, you may want to consult directly with a local attorney who specializes in these type of cases. They can best advise you as to specific state law. If you fail to follow the correct legal procedure, your children could potentially sue you for unlawful eviction and possibly more.