Agreed with Gabe Sanders .  The contract would be for both.  You don't get paid on sale till the title changes, so you are also placing the rental.

Compensation is based on what is offered. There are all sorts of arrangements.

Most is courtesy meaning the agent who showed the home, gets no compensation.  The ones pay 2.5-3% are often over charged rent. Only realtors understand how realtors work hard will compensate buyer agent $100-$500 ish.

I had one renter who owned 4 other homes wanted the listing agent pay him 1 month of compensation. 

I always thought 50% of 1 months rent.  In our market I see anywhere from 25%-50% of one months rent.

Those terms are all negotiated and written into the contract.  There are a lot of variables to take into consideration and that is why an attorney is usually recommended, unless your state has promulgated forms for lease purchase offers.

It depends upon the terms in one or more of the Buyers Representation Agreement, Buyers Customer Service Agreement, the MLS co-operative fee offered, and/or other agreements etc.

As with any commission, it is always negotiable.  When I was an active agent, I did a number of lease/purchases.  Generally, there was a non-refundable option payment (like a downpayment).  I took a portion of that, depending on the total dollar value of the sale and other factors. The balance was due at closing.  You must take an upfront fee on the option money because many (most) lease/purchases never close.  I never wanted to mess with collecting money on the monthly lease payment.

lease is a tad diff than lease purchase. we see 1/2 month to one full month. on a lease purchase, 1/2 month and then if sold appx 2% at transfer time

It's all about the contract.  The terms should include what happens should your client buys the home and it must have an expiration date.  The terms will be enforceable including the commission if all parties sign the agreement.

David Barr From my experience you get compensated when the property closes. You may want to ask for compensation on the lease. You probably won't get it, but it won't hurt to ask. Ask that the fee to be taken off of the sales price compensation. You never know until you ask.

Depends upon how the lease is drawn up and any agreement between brokerage firms. 

From the seller most likely as others have said minimal 100-800 be my guess. For a lease purchase I have negotiated it beofore that the buyers paid me 2% commission of the final purchase price.

Whatever is showing in MLS. It can be a % or a flat fee. Normal here is 25-35% of first months rent amount, or it could be $500.00 on a $2000.00 months rental for lease, and terms on the purchase can be included in lease. Many times the person leasing never follows through with purchase.

I most often see 2.5-3.0% of the first year's rent.

I also see 25-35% of the first month's rent.

Occasionally, I see $50.00-$100.00, which the listing office calls a referral fee. 

Minimally - I've seen as low as $100 in the MLS offered as co-broke.