Hi ya and welcome to the forum :2thumb:
Do you know what species (type) of tortoise you would like?
Most species are best suited to living in an open topped tortoise table but not all of them, some are best suited to living in a vivaruim (tank)
A tortoise table is basically 4 deep sides and a bottom, normally made of wood. There is no top on it so that airflow and circulation is good.
Also would you like a species that hibernates or one that doesn't?
Tortoises live for over a hundred years
At the top of this page there is a sticky called 'Housing' have a look through there and you can see lots of different tables that people have built - this will give you lots of ideas on how to decorate them etc., As long as the sides are nice and deep (about 12-18" deep) the tables are totally safe.
All the species are different sizes when fully grown, from about 8-10" right up to 3 feet.
Do you have an outdoor space at all? The majority of species do benefit greatily from being outside and you really do need to have an outdoor space that you can use to make a safe enclosure/penn for the tortoise.
Hope some of that helps hunny : victory: