They share in sale proceeds equal to their pro-rata investment.  

Thus it limits a high-income individual's (like @Andrey Y.) ability to contribute to a backdoor Roth IRA to a pro-rata basis rather than the full annual limit ($5,500/year) unless he's willing to convert the rollover IRA into a Roth and take the one-time tax hit.Out of curiosity, do any of your investors with 1099 income use solo-401k's to fund their real estate ventures?

Generally only units are sold to purchasers with a pro rata interest in the common elements and a exclusive right to use the limited common elements servicing that unit coming with it. 

@Antonio DeFlorioI've also seen:Buyer to pay for survey and provide a sealed copy to seller.Buyer agrees that their attorney has reviewed the contract and accepts all terms.All contingencies waived.Should seller decide to appeal previous year's property taxes, buyer is to pay their pro-rata share of the legal expenses to do so.Like you said - buyer pays all closing costsAnd all of these things are always buried in the middle of 16 pages.

Obvious reasons for this is to deduct all expenses and not do a pro-rata allocation of expenses. 

If so, you might want to get a separate meter so you can charge them for their entire use-instead of determining a pro-rata share.

You can't charge them for uninhabitable days so you would rebate rent pro-rata for those and cancel the lease.

The parties agree that the monthly rent set forth above shall be increased or decreased pro rata (effective January 1 of each calendar year) to reflect any increase or decrease in real estate taxes.

The other 50% is split pro-rata amongst the investors so you get 10% of that 50% and each other investor gets the amount invested divided by the total invested by everyone (which establishes an ownership percentage) multiplied by 50% (the total investor share).

Then you have to figure out pro rata and pro rated amounts when tenants move out at weird times.