This has doom written all over it.
No way is he ready for a relationship after 25 yr relationship/split and a home and business to sort nor does it sound like he wants one but he is being dishonest by hiding behind his 'busy life.' Everyone's busy - if you're really into someone, you make time and you value them enough to call it a relationship, not treat like them some ever-ready shag on the side when you fancy it. He is using you.
Is your self esteem so low that you'll wait around for him to 'give you dates' he's free then you'll jump to it? You are already working around him but you're not even in a relationship together? That is co-dependence and you should examine why you think it is ok for you to be treated like this. You are not some desperate saddo waiting by the phone for him to be at a loose end and nothing better to do so he phones you for sex/dinner/walk and you go running. That says your life is empty and you'll always be available to him. People will treat you how you let them treat you.
To him, you're a shag on the side until something better comes along. He won't admit to looking or keeping his options open but that's what he is doing. Sorry to be blunt but that's the reality.
He is effectively telling you his time and his needs are more important than yours and he's terribly busy and important and you're not and can jump to his command anytime. It's not your problem that he's got no stability in his work or housing, neither should you compromise your life to fit around someone who openly offers you no commitment. Fuck that. He is taking the piss royally.
Walk away before you get in deeper and get really hurt. You deserve so much better. You are not someone's commodity to be used at their command and to plug the gap while they get through the rebound phase and sort the fallout from their old life.
Instead of him telling you he doesn't want a relationship, you tell him, you don't want one with someone who thinks it's ok to treat you this way and either it's a relationship or nothing. And why would you want to be 'friends' with him?
Don't mistake 'honesty' for treating you like a mug. Just because someone has the brass front and thinks it's ok to tell you upfront that they plan to treat you like a mug and see if you'll wear it, does not make it ok.
Tighten up your boundaries. Be unavailable when he calls to offer you a crumb of his precious time. Be genuinely busy because you have a life and plans and goals of your own.
No relationship, no sex, no dates. Don't fall for the friends with benefits routine, that's not what you want.
And start dating other people, you owe him nothing, no loyalty, no explanations, no commitment.
Save your sanity and walk away.