@Zach Ziskin
Here are two reasons to have contractors submit bids.
First, you get a detailed punch list of items that need to be repaired or will need to be replaced/upgraded in the near future. You then use that list to determine what you can do and what will need professional work. It gives you an accurate CapEx reserves determination.
Second, it provides solid ammunition to justify a discounted purchase offer. You have greater negotiating power with the Seller.
As far as making offers based on photos or even sight unseen. How do you really know when the photos were taken. Do you think the Seller will show all the problem areas? Let me give you an actual example.
I went to look at a duplex (2 - 3 Bed/1 Bath) on a 3/4 acre lot. List for $100K. 3 pictures were provided (Front street view, 1 Bedroom, 1 Kitchen). All looked decent and clean. When we arrived the first thing you see is the property was completely overgrown with vegetation, 2 foot high grass and weeds, large dead limbs hanging from trees, one even on top the roof. The exterior needed a complete makeover. The roof was more than likely damaged from the tree limb. When we entered the first unit it had a strong odor of dog urin and cigarette smoke. Kitchen cabinets need repair/replacing, as well as most rooms needed something. The second unit was worse. It apparently had water damage from the roof leaking. It had been gutted and the work had not been finished. Far from it.
The detailed SOW and bid we developed provided more than enough justification to purchase the property at 50% of the list price. The Seller really just wanted to get rid of a problem property he did not have time to mess with.
Of course there are numerous other hidden problems that cannot be detected from photos. Like foundation s, septic systems, HVAC, to name a few.
My advice is not to go that route. Stay conservative, be thorough, do your due diligence, and you will be more successful and profitable. :)