:Class A Properties:Cashflow vs Appreciation: Typically, 3-5 years for positive cashflow, but you get highest relative rent & value appreciation.Vacancy Est: Historically 10%, 5% the more recent norm.Tenant Pool: Majority will have FICO scores of 680+ (roughly 5% probability of default), zero evictions in last 7 years.Class B Properties:Cashflow vs Appreciation: Typically, decent amount of relative rent & value appreciation.Vacancy Est: Historically 10%, 5% should be applied only if proper research done to support.Tenant Pool: Majority will have FICO scores of 620-680 (around 10% probability of default), some blemishes, but should have no evictions in last 5 yearsClass C Properties:Cashflow vs Appreciation: Typically, high cashflow and at the lower end of relative rent & value appreciation.

If your current lender is open to restructuring, you could negotiate better terms (lower rate or extended term).

The Heloc can also pose as a debt obstacle since its an open end mortgage a.k.a credit card.a mortgage is also set up over 30 years so it offers a lower rate and payment. 

So when I get multiple bids and one is significantly lower, I don't think of them as a deal.

The estate agent tells me that banks normally undervalue their valuations and that it is great that the valuation is so high (while still being lower than the asking price!)

I haven't heard of that company, but if you are looking for done-for-you real estate investing then just know that your returns are going to be significantly lower.

We have made money buying properety based on cash flow (lower priced) rented out for a period, then selling to an owner occupant. 

Seems like it'd be lower maintenance since it's a new build and in a nice area.

I think the engineering issues on them have been resolved.I've used a number of different brands (lower price point) and haven't had issues with any of them.

She's also likely to be causing your tenant in the lower unit to have a higher heating bill.