So how would you accurately calculate ARV then?

Now I have plenty of methods of gathering contacts, I have lots of family and family friends who I could honestly probably have as contacts so that's not the issue.

So what I can gather so far is...1.

The information the prospective tenants provide won't necessarily be accurate. 

From what I gather, there is a lot of demand for houses.

But neither can be accurate if they don't take into account the floor plan, condition of the mechanicals (electric, plumbing, HVAC) and structure (roof, gutters/drainage system, foundation, doors, windows, walls, woodwork, special features) and furnishings (cabinetry, floor coverings, window coverings, appliances, lighting fixtures, plumbing fixtures) and land (zoning, location, yard size, landscaping, fencing, nearby attractions/distractions).

@David FernandezTechnically your boiler is an HVAC system (heating), but I gather you are contemplating replacing the hydronic heat with forced air.If the property is in an environment where there is a significant cooling season, then the extra cost of switching to a central air handler (i.e. heat pump w/ ancillary gas for additional heat), removing the radiators and lines and installing ductwork may make longterm sense.If there is not a significant cooling season, then it would be far more economical to replace your old boiler with a new high-efficiency condensing gas boiler (~95% efficient).  

I'd recommend reading Garrett Sutton's, "How to Start Your Own Corporation" as a way to start gathering info on what you need to know.

@Jd Martin  Portlandia is absolutely dead on accurate as to how PDX is.. really .. you would have to come here an experience it for yourself..

Are you trying to gather the possibility of other uses?