I think we have a bit out of topic. My post was not discussing what investment is a good investment or should I join an investment that  was  being discussed in kopitiam .

My topic is : is it doable if there is an agreement govern a group of 5 same mindset/goal stranger to buy a property and dispose a property? And, what kind of risk would we face? how could we solve it?

I agree with you that it is the best time to realize the investment when everyone is discussing it.

There is no such thing of S&P of 5 people that can force out 1 owner if he/she fail to pay the installment.

S&P is between the purchaser and seller to facilitate the sales of property, once executed and the property title being transferred to the buyer, that's the end of the S&P function.

While, ownership right of the property is on the property title registration.

If hold through the company, the subjected to company law, you just need to get more than 50% approval during the resolution of the company to sell off the property, then the property can be sold already, instead of need all 5 people to sign off the sale of property.
And the proceed of property selling is back to the company, instead of individual.
By then how to distribute the money, then it is under company regulation.

S&P is a legal document to facilitate the MOT of the property, aka between purchaser and seller issue, (not among purchasers themselves)

Why seller want to care to sign such an S&P in the first place, as it may complicating the MOT afterwards.

Somemore, the being "forced out" owner may able to challenge the legality of the agreement in the first place.

When a property already registered under his/her name or 2 names, then the property cannot be sold without all the signature required, except through bankruptcy liquidation, which is another story.

A lot of dispute arised on the joint name property, is because the property transfer need all joint owner to sign off before the property can be sold/rent, not simply any 3rd party agreement that can already make the property being transferred/sold without the need of real owner to sign off the MOT/S&P.

It is always good to have counter argument in such issue, which only raise awareness and benefited to all. 

POA also not workable in this situation.
You have A,B,C,D,E 5 people.

You have 5 people to sign the POA (which required to be endorsed by high court), mean 5 donor.
Who is the donee then?

If A is the donee under the POA, mean A has full in charge on the property.
By then, A can do whatever on the property, as BCDE already gave POA to A to act on behalf.
A become like "boss to others". 

Why BCDE want to sign such an POA in the first place?

Also POA is intended to act on behalf only, aka it may settle the sign off the signature related to the property issue,
but it doesn't settle the "force out" clause the intended for this case.
The proceed the selling the property still need to go back to the original owner.

Still a very messy situation.