Lawyers don’t write deeds.

Depending on current vesting, partner A may need to agree to partner B selling their interest. Will they ??

I have been involved with a few partners and all of them worked out well.
It is CRUCIAL that everyone involved understands vesting options and the consequences.
LINK:
http://www.firstam.com/assets/homebuilder/homebuyer/vesting-ways-to-take-title.pdf

**Based on your info, they would probably want TENANCY IN COMMON.
If partners are 50/50 there should be a clear understanding up front of how any disagreements will be settled;
otherwise the majority owner’s decisions are final.

There are possible consequences to any decisions & investments.
I know plenty of people who were so cautious and conservative throughout life and always focused on what could go wrong and never took any risks in life. Afraid of their own shadow.
Most of them have very little net worth today and their only income is around $1000 a month social ‘security’