Dental Hygenist Recommends Expander, Insurance Doesnt Cover Ortho? ?

I saw my dentist for the first time in 5 yrs(had no health insurance) and actually he wasn’t in so I saw his terrible dental hygenist she took x-rays/cleaned/examined..came out with a bunch of cavities(not sure of the # she said he might find more?) which doesn’t bother me, because genetically I’m pretty prone to them..She also mentioned I go back to my orthodontist(havent seen him in about 5 years also…) and get an expander on the bottom of my teeth if I could..(I have overcrowding since my wisdom teeth came in/not wearing my retainer..dammit.) Well here’s my issue, my dental insurance doesn’t cover orthodontics(wonderrrful..) and I’m not exactly rich(more like starving college student, whom mommy & daddy havent loaned me a penny since I was 13..) and I don’t know what to do..I’ve made the appointment with the orthodontist to get a permanent metal bracket on the back of my two front teeth put back on..(if he can, that happened almost 2 years ago)..and I don’t want to mention the expander and have him start doing things and not be able to pay my rent this month..What should I do? If I don’t get this expander, will my dentist just stop seeing me?