The best way to determine repairs is to have a rehab contractor go through the home and give you an estimate. That will cost you money and most won't do it unless there is some sort of agreement that they will be doing the work.
The only good, cheap, and reliable way to determine repair costs is to learn how to determine repair costs. Do it yourself. There are a few good books on the subject. You won't become a property inspector, but it will definitely be more reliable than not knowing anything. My advice would be to estimate on the high end of your assessment if you aren't absolutely sure. If you are wholesaling, determining the deal depends on how much profit the buyer gains after repairs. If you estimate a bit high, it just makes the property cheaper for the buyer.
Estimating ARV is on you. The basic idea is that you are using comparable houses sold nearby to determine the value of the subject property after all repairs have been completed. You can learn how to do this in threads on BP, youtube, and various other free sources. You could have a licensed Agent who understands REI run the numbers for you, but you should know how to do that yourself. Besides, I'm sure they would eventually get tired of doing your work for you.
The information you have there won't help determine if it is a deal or not. You absolutely must have the ARV and repair estimates. Without those, anything could or could not be a deal. Those are the PB&J in your PB&J sandwich.
Now that I have answered your questions, you need to do more research. This is information that you should already have before you decide to pull the trigger on any REI strategy. I recommend drowning yourself in BP podcasts, threads, and books. Watch some videos. Just get as much info as you can.
Also I want to warn you about posting questions on wholesaling. Make sure it is information you absolutely cannot find by reading other threads. There is a Coke vs Pepsi verbal war on wholesaling here. They will hijack your thread to argue about wholesaling legality and equitable interest.