I've done all the Pro-city epics. The bit that takes the longest is raising Faction sympathy. So when you change factions, try and change in an order that you next faction is allied - as you will get a +10 FS bonus when you change faction.
Before I came to FA, I've already had done the Tangent Epic. I then switched to NExT and did that epic over one night, before heading to Techhaven to raise FS to join FA. Before Christmas I went on an epic spree, where I went from FA-CM-CA-DRE-BT-PP and back to FA. I spent about 1.5 million, as I was lucky enough to know a lot of people who didn't mind being killed for the epic.
Also if you are below rank /45 you can drug up to get above rank /45 - as you need to be a certain rank to do each part.
Fallen Angels Epic - this is a temporary epic, in 3 long parts. Reward is a DoY Raygun, but it's not a proper epic item. It will drop in your quickbelt, and also it cannot be repaired to 120/120. Only reason I'm a FA master, is to show my loyalty to the Faction.

You only need the master status to activate the clan key. I have a few members in Phoenix, who are master's and I'm sure if you ask nicely and wave lots of cash at them, I'm sure the will activate the clan key for you. However, the master status will be reset come DoY.
City Admin Epic - Pointless if you are not going to stay in City Admin, as the Power Armour can only been worn by people who are a member of CA. Also you need STR40 to wear it, so that rules out the monk. Tricky bit is arranging 3 TG kills, and also killing the copbot down Regents with all those warriors down there. Note when you do this epic, note the brainwashing and propaganda methods it uses.
Diamond Real - You get a nice storage cell either located in Outzone, or if you are lucky, Plaza 4. It has about 15 cabs, so great for storing all your junk. Tricky bit is knowing your way around the Black Dragon guards for the last part.
NExT - You get a indestructable Reveller - to me, the most useful epic item. No epic kills needed on this one either.
Biotech - You get a move-on chip - useful for Gentanks. Tricky bit is getting to Loba village, as that sector was swarming with DoY bots...and they shoot Biotech people as well. Best way to get they is ask someone with a Rhino to get you there, as that can really soak the damange.
PhotoPharm - You get the nice PP chip - nothing too hard about this epic, just a lot of walking around. And getting an FA kill is quite easy.
Tangent - This evil faction gives either a rifle/pistol or cannon. Epic is easy enought, tricky part is part 3 I think, when you have to get to Catlock bay. Also when the epic text says kill 2 biotec, you only need one kill.
City Mercs - nice useful gat-cannon if you are a tank. I found this epic to be the most entertaining. Nothing too hard on this epic.
To be honest I say do all the Pro-City epics now before DoY, as post DoY I reckon doing them will be harder. And besides the story line on some of the epics is good fun.