I sometimes encounter Monero transactions with more than two inputs.
This is very common and happens automatically. Your wallet uses outputs it receives, as inputs to fund a transaction. Sometimes your wallet will need to use multiple outputs (as inputs), to fund a transaction. This however is different from your question:
If I have access to multiple ...
I'm running up to 3 monero daemon's on an very old laptop. 2 GB RAM, 240 GB SSD.
Plus 3 heavy Nodejs apps, Apache, MySQL, MongoDB, Redis and sendmail.
Once a daemon is synced, the CPU and RAM usage is very little.
Linux Kernel 4.4.182 #1 SMP x86_64 Intel(R) Core(TM)2 Duo CPU T8100 @ 2.10GHz GenuineIntel GNU/Linux
On one of my boxes, monerod is using 1.2GB RAM, and on another 2GB. Both of these are Ubuntu. Of course, you'll also need a hard disk, ideally SSD, with 30GB+ free for a pruned node or 80GB+ for an unpruned node.