Metal Detecting Questions Prior To Buying A Detector

I recently found a 1926 Buffalo nickel in the soil when digging up some old bushes near the barn on my property that I bought recently. I also found a strange hidden compartment in the foundation of the barn that may have been used at some point to store something valuable although it was void of anything good in it when I removed the soil from it and inspected it.

My 80 year old neighbor told me that the house that was built in the 1890s was originally where the barn is now, and that when it burned down in 1946 that her neighbor decided to build a new home in the location where my home is now, and that the barn was then built on the foundation of the old house.

I am curious as to if there are any other coins hidden on my property and here are my metal detecting questions:

Can a metal detector penetrate through the concrete floor in the barn to the soil under it which might have valuables that were in the fire under it?

Is the garret ace 250 a good metal detector or should I get a different model? The garret ace 250 looks to have features needed to look for only gold and silver and exclude other metals.

The guy who use to live here until he passed away in 1984 was a mechanic/machinist and there are all sorts of nails, bolts, washers, and other metal junk embedded in the soil. Is this going to be a problem for detecting silver and gold items that might be in the soil where its unlikely that any gold items are there, but very likely that silver coins could have fallen out of pockets and are tucked under a clump of lawn?

The last metal detector I owned was a cheap $90 piece of junk off of ebay from china. It gave a tone for metal, but you had no idea what it was until you dug it up. Lots of wasted time digging up pull tabs, nails, bolts, pipes, broken toy cap gun, matchbox cars, foil wrappers, aluminum foil, and part of a fireplace damper that was patent pending 1851 in the woods with only a few 1950's wheat pennies found near a lake about 4 inches down in the soil. I ended up giving this junk metal detector away to a co-worker who needed to check trees for embedded nails and barbed wire before taking a chain saw to trees that he cut down as for he almost lost a hand once when it caught some barbed wire that was hidden in the trunk and it kicked back on him.

My budget for a metal detector I was hoping to be less than $300 however I can spend up to $1000 if I wanted to, but would like to stay in the $300 range if possible.

attached is a picture of the nickel and the hidden compartment that didnt have anything good in the foundation of the barn. There was a piece of angle iron resting in it hiding the compartment from view due to soil level just about to the top of it, and while pulling old bushes out the crack in the foundation of the barn brought my eye to check into why it cracked. When removing the angle iron I saw there was a compartment that didnt seem to serve a useful purpose for the barn. I then used my wifes gardening hand shovel to carefully dig out the dirt from it in which it is a compartment about 12 inches wide by 10 inches tall, by about 18 inches deep and leads to the poured concrete floor in the barn and stops there. It serves no specific purpose and so my thoughts are that it was used to hide valuables possibly since after a fire, the prior owner may have realized that a foundation is fireproof, as well as many who went through the 1930s depression era hid money in places in walls etc.