1) The Trailer wouldn't be counted on the appraisal towards the value or in rents. The 3/1.5 and 1/1 would classify it as a duplex so the down payment on a Non-Owner Occupied 2 unit is 25% which on 70,000 is 17,500. So Cash to close would be $17,500 plus closing costs.
Your PITI on a loan amount of 52,500 and I threw a 4% rate on there would be about 250.64 Then add Insurance + Taxes + Property Management would bring you to roughly the 650 range. From that point you are cash flowing 750 per month between the 3 units
2) If you want to see the property then sure go have a look but more so I would recommend a Property Inspector goes out and gives you a full inspection of the property. They will look it up down and be able to tell you repairs that you have to look forward to that may not come up in the appraisal.
3) Get a buying agent they are paid by the seller and represent your interests
4) Non-Owner Occupied Conventional 2 unit is 25% Down
5) Anything you are missing will come out through the Inspection and Appraisal
Best of Luck!