I can imagine the difference in commission for real estate agents. 

I can imagine rent checks could get addicting!

I imagine the  Architect next door is the Go to Guy here.  

Once you get to that certain level I imagine it's a whole different business that you're dealing with but more beneficial.

Sale ContractReal Estate Transfer Disclosure Statement (shouldn't be many given that it's raw land)Natural Hazard Disclosure StatementCredit Information Form (I am open to financing up to 60% of selling price)Installment Land Contract (If I do indeed finance the property)Offer To Purchase Real PropertyCounteroffer To Purchase Real PropertyAcceptance Of Purchase OfferDeposit ReceiptContingency ReleaseI imagine a Title company needs to be involved to assist with processing the change of title documents and hold funds in escrow.

I would imagine there is probably some steep competition if is a public market posting deals like that.

I come from a commercial construction background and 5% is the normal fee for architects for commercial work so I imagine residential is similar in fees.As @Chad Conrad pointed out, you need to have a designer that is aware of codes.  

You'll also have to be careful about what you buy and doubly ensure your tenants are strong enough to survive the outfall.I also imagine there might be some motivated landlords eager to get out.

I'd imagine that it would be easier to terminate and/or add new properties that way.

., I would imagine that a bulk discount would be available, but if they are working fine right now, why replace them?