I was wondering if anyone has any advice on how to boost the curb appeal of this house i recently purchased?

You will think Marshall and stuff thrown out on curb they will be gone and locks changed.Then a few days later will find they have moved into your other unit downstairs with them.

And some nice curb appeal and new paint.

Siding, More Space, Curb Appeal Etc ...Which ones bring the best return on investment?

A bit of landscaping, perhaps a picket fence, and a pathway to the front door would go a long way to adding curb appeal to the property and attracting better renters.

look into the spyder tubular skylight, you may be able to get both lights from a singular roof opening, and use at least a 6" high curb,,, see local recommendations and codes

This is also your first point at which some degree of error can be introduced, as AVM's are typically based on public record sales, and public records don't include attributes like view, curb appeal, and other less tangible items that can effect price.

One of the houses has a horribly maintained yard but is a blank slate - is it worth investing in landscaping to raise curb appeal?

Quick tip: When we evaluate a vacant lot, we look for curbs, manholes, and driveways.

Moreover, if the window unit is my only option, how have you made it look more appealing from the curb as well as the inside?