All good comments. Most of the time, lenders doing 2-4 family properties seem to want comparable rents (its on the 1025). However, they don't always want an operating income statement. I charge a little (slightly) more than you do for it. Because the fee is built in, I don't charge them extra for the comparable rental data. That data can usually be found in the listings for the properties I am using as comparable sales and comparable listings anyway.
For other properties, it gets a bit harder. Our MLS does not list rent amount on SFR's, so unless the agent puts it in the comments, you won't find it. These are like gold and everytime I find one I put it in a database for future use.
Most of the lenders I've worked for want a comparable rent schedule when doing an SFR as an income property. For this I charge extra. The best source of data I've found is a couple of local agents who double as property managers.
Finding properties that were rented when sold- now that's another issue. I have long held that it should be possible to do an income approach on an SFR in a similar way as is done on many commercial properties; by analyzing the market rent and capitalizing it with cap rates derived from competing investments. However, the appraisal industry (and the client base) seem to be stuck on the idea that the only way to get a good opinion of value is from GRM taken from properties sold while rented. I don't doubt that that is the best way when the data is available, but when it's not I feel like there should be alternatives. However, to date, I have never seen an appraiser use any other method and I don't really want to be a trail blazer. Any comments?