Keith and Teresa have given great advice on this.
I just want to add one more piece of advice when buying lots in Lago Vista.
The Property Owners Association owns the parks, boat ramps, and amenities. Not all property on Lago Vista is part of the POA plats. Be sure you get an agent who will check on whether you are buying a lot that is included in the POA. There used to be optional membership for our homeowners who did not own POA platted lots. When this was terminated by the POA, participants were grandfathered in, but once the property is sold, the new owners aren't eligible. This can be a nasty surprise if you were counting on lake access through the parks.