What exactly are we receiving from being a member of a Legion for resources? Should there be some sort of message detailing what we get when the timer is up? Could some people just log in and leech off other people then?

Right now, people who are active (logged in in the last 24 hours) and have been with the legion for over 1 day are eligible for shipment of resources. How much (if any) you get is dependent on how your legion is set up. The options currently are:

Divided Evenly Between all Eligible Members
Divided by % of Base Upgrade Contributions.

Once a day on your news page, you should see something like this (if you are eligible).

Base resources are split evenly between eligible players. Which players are eligible is determined by the rules set up by the leaders of your legion. If you are eligible, resources will be deposited into your cache once per day, and it notifies you in the ship log. Mine looks like this:

1 hour, 24 mins ago
Sukram has disabled Stalar Command Center! | Tell Your Friends
Sukram gained: T.O. Harmonic GigaPulser (artifact) 300
Randy Manning gained: T.O. Force Barrier (artifact) 330
Trevlain gained: T.O. Harmonic GigaPulser (artifact) 300
Llore gained: T.O. Harmonic GigaPulser (artifact) 300
Asteria gained: T.O. Force Barrier (artifact) 300
Mahargcire gained: T.O. Force Barrier (artifact) 300
XxInstigatorxX gained: T.O. Force Barrier (artifact) 300
1 hour, 24 mins ago From: Nocifer Deathblade
Nocifer Deathblade asks for your assistance with the following enemy: Silthion Queen
1 hour, 34 mins ago From: Chrace
Chrace asks for your assistance with the following enemy: Dark MegaComplex
2 hours, 2 mins ago
Llore has disabled Reynard, Lazuli Titan! | Tell Your Friends
Krauzen gained: Lazuli Parts Vault (artifact)180
Asteria gained: Lazuli Parts Vault (artifact)180
Llore gained: Lazuli Mind Controller (artifact)180
2 hours, 3 mins ago
Reward Claimed
You acquire a Tri-Matrix Emblem Artifact
View Your Cargo
3 hours, 6 mins ago
(1) Daily shipment of Legion Base resources arrived:
1812 Mineral Units, 3590 Research Points, 3590 Artifact Points
(Total Divided Evenly Between all Eligible Members)
3 hours, 23 mins ago From: Asteria
Asteria asks for your assistance with the following enemy: Reynard, Lazuli Titan

Bah ODragon beat me to it

We're both being so nice and helpful... what's up with that?!?

Can any of you tell me what the cost/size/performance of the upgraded production buildings are?

Thanks for the 411 guys!