Then get an estimate for someone to come out and fix it. 

I am getting estimates on replacing a old oil boiler with a new gas boiler to heat the rental house.

As such, I am trying to understand how to objectively estimate a properties value relative to the area - I want to stress both the objectiveness and relativeness of this.

@Matthew Crivelli our combined income is estimated around $15k a month, maybe a bit more.

With 2-4 units, if you don't have a huge portfolio or if you have a good PM it isn't unreasonable to have a tenant lined up to move in the day after your existing tenant moves out.PM: Instead of using a market standard like 10%, I'd get with a PM company and have them estimate a property that is similar to what you are looking to buy.

Simply reach out to several contractors and have them provide an estimate/quote for each repair item.

If not there are resources to get a good estimate. 

Since this is our first investment property and we're out of state, we'd like some advice on general estimates or contractors who can come out and check out the place if possible!

Buyer, at Buyer’s sole discretion, may accept theplan of242 remediation, terminate this Contract, or allow the Seller to escrow one and one half (1 ½)243 times the amount of the bid or written estimate, as determined by the Buyer, of such244 environmental repair(s)at Closing.

The numbers:Property value: $421,000Mortgage: $241,000Potential cash from sale: $154k (after fees)Potential gross rent: $2,100-$2,300 (used $2,200 for calcs)Potential net rent: $277/m (excluding equity gain on mtg)Estimated monthly costsPI: $1027Property Taxes: $233Home/Flood Ins: $112PM (10%): $220Vacancy (5%): $110Maintenance (10%): $220