I highly recommend people read the translation project volume 1 --- it lays out the nature of their initial relationship pretty clearly, Horo's complex feelings, Lawrence's internal monolog, etc.
He's thought through the angles, but there's one bullet item on his list
where he thinks it'll be nice to sleep next to someone that cuddly looking (even if sex isn't involved). He is alone so much traveling that just the companionship is desirable.
They both enter this arrangement with eyes pretty wide open (though Lawrence is foggier on the ramifications into the future
). Wonderfully practical and "grown up"...