You can either request the lock box combo or if the house is vacant or boarded, tell them to look through the windows or pry open a board. Let’s face it, if the house is boarded, there is a strong motivation to get the house sold. Good Luck
I have been studying Ron LeGrand’s Flipping course for awhile, and in it he suggests to have potential buyers do a ‘drive by’ of the property and if interested (from just seeing the outside) to call him back to purchase it… how realistic is that? - would not most rehabbers want to look inside the property before buying? and would this not tick off both the original seller and your realtor (assuming you follow LeGrand and use a realtor to find these properties.) - finally, would this not ruin a potential simultaneous close that you were trying to arrange?
In Ron’s course he recommends using realtors to find foreclosures, etc… however, he does not cover how to deal with realtors when your buyer wants to view the property (that you have placed an offer to purchase).