Turnip storage is an issue. Anything left outside can be easily picked up by other players. Storing turnips on my floor at home is a much better option. I want to fill my house to capacity with turnips. How many turnips do I need to buy? How many trips to Daisy Mae do I need to make?
TLDR; 29,200 / 292 bundles / 8 trips to Daisy Mae
We'll assume that your house is maxed out and that your pocket storage is also maxed out.
Here are the measurements of a maxed out home:
- Basement: 6x10 = 60
- Upstairs: 6x10 = 60
- Left-room: 6x6 = 36
- Right-room: 6x6 = 36
- Backroom: 6x6 = 36
- Front-room: 8x8 = 64
There are 292 floor spot in your house where you can put your turnips.
Which is 4,000 turnips, as each bundle has 100 turnips in it. You will have 280 bundles of turnips after seven full trips to Daisy Mae; you'll need to make an eight trip to buy the extra 12 bundles.
An alternative to this problem,
Anything left outside can be easily picked up by other player.
Place a fence around your turnips.
While someone is visiting your island, no one (including you) can pick up fences (as well as "placed" things). This ensures no one will be able to get into your turnip field.
The only incredibly small caveat I can think of is that hackers may be able to no-clip through fences but the game itself may prevent anyone from picking up things in your house. But I think the chances of running into a hacker who wants to troll you like this is pretty small. Because if they are hacking they can already get as many bells as they want.