Thatched farmhouses are now 300 gilda (previously 50), so probably not worth it at the start. There are more important things to spend gilda on in the early stages.
Almost every house can be upgraded, including 16×16 houses. Upgrading a 16x house gives you 2 seed beds (better than bundles and aren’t affected by climate) and an upgraded thatched gives you 2 seed beds + 1 other specialty harvesting thing depending on the design (another seed bed, livestock pen, or mining drill.) Three random plants grow on an upgraded thatched every day, which can include Clubhead Fungus.
24×24 & 28×28 houses don’t get special harvesting things. Instead, they turn into specialty crafting houses (fertilizer pack maker, equipment crafting, or food/potion crafting).
These aren’t particularly cheap. For example, the 16×16 house upgrade costs 900g in vendor materials (6x building management titles), 40 stone construction bundles, 20 iron construction bundles, 20 wooden beam bundles, and 5 enchanted blueprints (break down housing patterns with evenstone for these).
When breaking down building designs for enchanted blueprints, just break down the 15 gilda star 16×16 houses. It’s wayyy more efficient. The game gives you blueprints = gilda cost of design divided by 10 (rounded up). For example, a 15 Gilda house gives 2 blueprints, while a 50 gilda house gives 5.
Upgraded houses also give the owner daily quests for either vocation or gilda.