One of the things that seems to be an area of confusion regarding truely tender trees that will not tolerate frost are also suitable for growing indoors only.
This simply aint so. Now I can find people who will grow ficus indoors year round, and they are welcome to it.
Most tender trees need a residence outdoors from May till October in zone 5-a and south. Among those are:
Japanese azalea
Pomegranite
Olive (olea europa)
Texas Ebony
Citrus
I'm sure others will amend this list.