Orion will not carry humans on board until 2021 at the earliest. Dragon is ready now. It does not need superdracos installed.
Bigelow modules are overkill. ILC Dover could provide Dragon with a 2000kg porch providing perhaps 50m3 of volume. Dragon mass is 4200kg.
A crew of two will require 4000kg (4m3) including themselves and consumables with no recycling assumed. Altogether that's 10200kg.
F9 can put 13000kg in LEO so more luxuries could be added. No SLS or FH required.
If you stop considering SLS & Orion you can use stuff that already exists so you can stop worrying about being able to meet the Jan. 2018 date.
The F9 upper stage would mate on the ground but the crew would have to wait in orbit for the refueling. We need to have experience refueling in orbit for future missions. We might as well put that milestone behind us now.
The TMI would happen before inflating the porch afterwhich cargo would be moved to provide plenty of space including some for privacy.
It doesn't cost a billion and it doesn't have danger of being delayed if they start now. Tito needs to forget SLS and Orion.
Update: NASA's response to Tito...
"Inspiration Mars' proposed schedule is a significant challenge due to life support systems, space radiation response, habitats, and the human psychology of being in a small spacecraft for over 500 days. The agency is willing to share technical and programmatic expertise with Inspiration Mars, but is unable to commit to sharing expenses with them."Like I said.
Update: I'm curious to see what reaction this post gets?