If I sell my property and I hold a second mortgage, and the buyer takes a first mortgage on same property, can the buyer increase the amount of the 1st mortgage withour informing me, the holder of the second mortgage?
As long as you have recorded the second mortgage with the county as a lien against the property, the answer is no, buyer can't refinance without your consent. That formal consent is called a subordination. If you failed to record the 2nd mortgage (if you haven't done so already, need to do ASAP!), you have no recourse against a refinance that has already occurred.