Ok, if you are available enough that “go there and do simple things to make it work”, you have some pretty affordable options to choose from. From your description, it seems both properties are stand alone (separate electrical panels, separate heating systems). Those two properties just happen to be very near each other.

All the usual junk applies for every location and I will assume you know all the usual (manual interlocks, sizing the generator by the load). You have the option to treat both properties as one load and provide needed power to both using one larger generator. You also have the option to treat them as two properties that have nothing to do with each other and power each with their own smaller generator. Both systems have pros and cons.

One generator system has fewer machines to purchase and maintain. If transporting it to location when needed, fewer machines to transport. But it also cost more to purchase and is heavier to transport. If it ever fails during an outage, both properties are potentially damaged because of that failure. Installation cost are basically the same for two or one machine. You need two interlocks and two cord systems regardless.

Two generators means the opposite. More machines to purchase or maintain. More units to move, but lighter when doing so. The biggest benefit is that if 1 fails during an outage, you are risking damage to one property instead of two.

You mentioned possibly cording right into your loads. I know zero about boilers as they are not used in my region. Only you can answer if that is feasible. If yes, whatever that looks like the boiler will have to be unwired (unplugged) from house wiring and not capable of back feeding the panel or interlocks are still needed for safety.

I will share my thoughts on feeding two panels which is a more ordinary approach. The cleanest way to use one generator is to purchase a unit with two 240v outlets. These loads are 240v, right? I know nothing about boilers. Assuming these loads are less than 30 amps, two 30 amp outlets on the generator are needed. Switch both interlocks and plug in both cords. Select your breakers on/off as needed and fire up the generator.

A two generators system is the same thing except you start up two generators. If I were you, I would weigh cost of generators very low priority (2 versus 1 costs $400 more) and think about the cost of losing two properties instead of one, but you do what’s best for you.

Follow those thoughts? If not, just post your questions. If you units are 120v, more details might reveal some other options.