Is their a minimum or maxiumum of the number of factions you can put into a deck. The rules seem to hint at 2 being minimum but I am really not sure.

Would a single faction be ok, or a single faction+neutral, or a 4 faction, for example.

I suppose there is no limit.

But if you play with a lot of different factions it could be difficult to manage the domains and especially the "matching ressource" rule when you want to play a card.

Yeah, there's no minimum or maximum number of factions to play in a deck. You could even go all neutral if you wanted (probably hard to do though).

You might note that one of the World championship level decks was a 7 faction deck.

.....Granted, many of the cards have had errata applied. But it worked once!

boss.sverok.net/CoC/CDA_rainbow2005.html

If you're using the full set of CoC CCG cards (i.e. all 1,000+ "legacy" cards) then a neutral-faction deck is not just playable, but (barely) competitive.

In general, there used to be certain cards that rewarded single-faction decks (e.g. low cost, powerful cards with a seven "Steadfast" requirement), but this LCG version of CoC might take a while before the range of available white-bordered cards supports powerful single-faction decks.

Often I've found that even if one faction is dominant (e.g. for a Mi-go themed Shub deck or a Criminal themed Syndicate deck) there are always just a smattering of other-faction cards which can make it better (Yog and Agency respectively, for the above decks). Again, this is based on the CCG, not necessarily the LCG.