An asset is anything that brings reward (usually income) with little effort. A waqf is an asset donated to the Muslims feasabilillah (for the sake of Allah).
Looking for an inexpensive asset to deposit continual good deeds into your akhira bank account? Try this: purchase an ‘itter bottle–one of the big oil ones–and place it somewhere in a masjid or prayer space. Or a kleenex box (especially if it’s winter or flu season). Or a book. All Muslims benefit from it, and you continue to earn the reward.
For a minimal cost, you reap massive benefit. Alhamdullilah. If you know any other inexpensive waqfs, comment them in inshaAllah. Jazakumullahu khayr.