I couldn't afford lessons if I wanted them, and by most standards, I probably could "use" them (I don't intend to show, and know enough to ride a horse on a trail - but, I probably don't have great posture, nor do I know all the tricks); I can, however, afford my horses. If a horse needs farrier work, I get the money - if I have to, I sell something. If a vet bill occurs? I get a loan.
I can't get a loan for horse back riding lessons, nor would I sell something for them. Your friend may be able to afford a horse easily.
I'd also like to mention that your friend probably won't accept your advice; no matter how nice you're being.