Great question! Storage is a key consideration for any residents, whether it be primary, secondary, or purely recreational.
When it comes to a movable tiny house, storage is at a premium for even the most critical items, so anything large, oversized, or otherwise unwieldy becomes a challenge to keep handy, yet out of our precious living spaces.
The first, and simplest, option would be to store items in the home, then when you arrive, place them outside. The area underneath a movable tiny house is a good spot for things you would like to keep mostly dry, and especially out of the sun. Likewise, the area under the tongue of a gooseneck based movable tiny offers the potential to create a secure storage box that can be added when the tiny house is parked. And enclosure is popular for RVs, and is a good option for gooseneck based tiny homes.
If you have yet to build your tiny house, giving storage lots of consideration during the design phase is key to living comfortably in a tiny house. Popular storage solutions within the tiny house include areas under the bed, and stairways. The storage loft is also a good consideration for items that won't return to the home dirty from use outside. For gooseneck and fifth wheel designs, creating a "basement storage" area underneath the upper floor level is popular in the RV world, and a great solution for kayaks, paddles, bicycles, camping equipment, and most anything else you can stuff into the unconditioned space beneath the floors of your home. A lien to might also be designed into the tiny house as and articulating shed roof, or prefab structure it you can assemble on site for long-term storage.
Storage buildings are the most ubiquitous solution, and a reasonable choice for a tiny house, especially as portable storage buildings can be relocated With a movable tiny house. Should the move be too far for the transport fee, portable storage buildings retain their value pretty well, and can be sold to recoup some of the money.
For those who are truly on the go, though parked long enough to keep items at hand, a small cargo trailer is a great choice. For the equivalent of an annual rent on the storage unit, a preowned cargo trailer can be purchased. This is our own personal choice of how to address seasonal clothing, occasional use items, and those we only need to access prior to long stance on the road.
A final consideration, and one leveraged by full-time RVers is to use a truck cap for items that might be needed during travel, or sports activities where you want to have something on hand, but not enclosed within the home.
Hope this helps you determine what would work best for you. Feel free to reach out to me directly, as the more we know about your second home, the more we could help brainstorm the most appropriate solution for you. Wishing you the very best.