do the space marines get all of their implants at the start or do they have to buy them with xp

Duh. It's part of the Space Marine Race - almost everything listed there under the stuff they get, especially traits, is from their Implants. In a sense this is 'bought with xp' in that they then get less xp to spend due to their headstart.

I tend to also allow use of the more esoteric implants as mentioned in DW as well, but that's just me.

Astartes implants are part of what makes astartes astartes. You might as well ask if a human has to take XP for it's spleen or whether renegades start with their left lung intact.

So yeah.

I really wish there was some options when it comes to the implants, though. Chaos Space Marines regularly suffer from breakdowns of some (or all!) of their implants, not to mention rampant mutations. While many loyalist chapters suffer from various quirks in their geneseed, the traitor legions is a literal cavalcade of chaos in that department.

Yet there are zero mechanics to support this.

Well, if you're a Heretek you might not want that left lung. All organic, messy and inefficient. It's not wonderfully perfect machine

P49, the little scrolly paperey bit on the bottom of the page explains the implants that all Chaos Marines (like their Imperial counterparts) have and their in game effect. It's as mentioned, assumed that these are implanted in the character at creation and included in the initial build without needing a cost.

One thing I thought was missing though is as Fgdsfg mentioned, some of these not working or missing. At the moment unless the GM wants to be difficult or the character asks for it, most of them seem in perfect health with all of them working. However if you did want to take some of these off someone, one of the Deathwatch Rulebooks (name escapes me at present) includes rules for custom Space Marine chapter creation and allows you to remove or have defective implants and explains the rough effect it might have on a Marine.

Well, if you're a Heretek you might not want that left lung. All organic, messy and inefficient. It's not wonderfully perfect machine

P49, the little scrolly paperey bit on the bottom of the page explains the implants that all Chaos Marines (like their Imperial counterparts) have and their in game effect. It's as mentioned, assumed that these are implanted in the character at creation and included in the initial build without needing a cost.

One thing I thought was missing though is as Fgdsfg mentioned, some of these not working or missing. At the moment unless the GM wants to be difficult or the character asks for it, most of them seem in perfect health with all of them working. However if you did want to take some of these off someone, one of the Deathwatch Rulebooks (name escapes me at present) includes rules for custom Space Marine chapter creation and allows you to remove or have defective implants and explains the rough effect it might have on a Marine.

Rites of Battle methinks that is... It has the custom chapter creation in it, which includes gene-seed troubles...