I am new to this game so this could be very normal but I got 15 houses in one tile. Is this normal or am I lucky?

lol if you mean the tile you start with that's normal, otherwise no houses can vary from none to maybe 3 or 4 on newly generated tiles as you expand during the match.

I haven't played in along time so that may have been tweaked, but still the first tile you start a session with always has about a dozen houses on it, and then afterward it's not generally more than a few per tile even in a session where they spawn on plenty of tiles iirc.

It's wise to cover every space possible around the houses int he starting tile with soaked up ballista gold, but then to only leave them in spaces where a ballista is soaking gold from two houses at once placing it in between them as you sell the rest to expand on further tiles. You won't want a large chunk of your gold consolidated right around the tower by the later waves with armor and shields.

I mean on a tile on round 23 I got 15 houses

There are some special tiles that can appear, ones with houses, ones with trees, and a few others. It's not uncommon to get these once in a while.

ok thank you guys very much