Wholesale deal turning into first home purchase!

[Edgar Aguillon]

I started a driving for dollars and got a few motivated sellers..now working on my buyers list. I found a lady who is really motivated to sell her house...Started crying since she grew up in the house but cannot afford to keep it any longer since she hates being a landlord...she inherited the house from her dad, so I was thinking about getting it under contract for a wholesale but turns out I really liked the area and rents go for about $650-$700 for a 2bdrm 1bath so I decided to take a trip to my local credit union to see if I can get a loan. They said they can approve me for a conventional with 20% down. The lady is asking $25,000, my uncle works for a construction company so he will be doing the rehab work for me. He estimated costs at about 13k-15k.i found a really nice realtor here in the area that estimated comps and ARV for me and said it's about 50-55k, my questions are how do I go about offering less to the lady for the house? Should I let her know it's based off of my rehab costs? And also would I need to get a realtor to help me through the process or can I just make a contract with my offer and if she accepts just take it to my bank?