You can go online and check the Fair Market Rents that HUD uses to the determine payment standard amounts for the Housing Choice Voucher (Section 8) program in select counties throughout the country here: https://www.huduser.gov/portal/datasets/fmr.html.  

Determine what your emergency fund (CapX) number should be, then fully fund it before you start taking money out.I know many in this forum don't go about it this way, which I also understand as well from a purely financial side.

My wife and I have a couple of our "dream" neighborhoods picked out. 

Once you know that, determine how long it would take you to cash flow/profit that amount.

I hope this post helps you in your determination.

If you don’t have someone then interview a few (not at the property) and arrange to show the unit to your top pick. 2.

If you could pick them up at 60-65% ARV (seller carry lenders typically don't have robust notes and deeds of trust, servicing notes, and pay histories) and work with the borrow to refinance at or near a full payoff, you'd make a killing.

You could contest it by providing the $350k comps you are talking about.You can pay for the full appraisal or you can also pick a different bank which will order it's own appraisal.

Can anyone advise me on the best way to determine the ARV for the home so I can establish how much of a loan I would need for the purchase and rehab costs??

I might have a couple contact for you, I'm connected with other wholesalers in different markets and just picked up a package of 5 SFRs myself to wholesale.