Actually the costs CAN vary greatly by part of country and time of year, also simply by what type of heating system the house has. Investors buying in these areas will already know about what these costs will be, and what rents are. For single family rental homes in your area, are utilities normally included in the rent or does the tenant pay? Is garbage separate or is it included in taxes? Average repair costs depend on the condition of the house when rented, and, frankly, the standards the landlord has. A good rehab before a tenant moves in should result in few necessary repairs. As for utilities, you might just ask the previous owner for copies of the past 12 months bills (although it is probably rare that the seller has these available!)
You missed three big areas that could amount to larger expenses than the other items combined--mortgage, taxes and insurance. In my part of the country the way taxes are structured, you can't go by what the previous owner was paying, depending on how long the house was owned, they might double, triple or even quadruple.
Again, if you are wholesaling to other investors who hold rentals, they will have their own calculations. They'll know by looking at the FMV and repairs required what price makes sense. Before presenting them with "deals" talk with them to see what they are looking for. At what price do they need to buy a house with a FMV of 100k to make sense for them? Most of the time it will depend on repairs needed to make it livable, taxes and insurance, and of course what the house would rent for.
Kim