If you have the land, and drainage a good underground shelter can be made with a overseas shipping container. These containers are 8 ft/10 ft high 8' wide and comes in lengths of 10, 20 and 40'. Buried under 3' of settled earth, these container would satisfy most survival requirements as most of them are water proof. Sprayed waterproofing on the out side before lowering will triple the life, accompanied with sprayed insulation will help keep it comfortable. With a few hidden vents, nobody but your most confided friends will know that it even exists. They sell for $2500+ depending on the size, shipping about $200-500 depend on the distance, or if your Claustrophobic it could make a good cabin made of corrugated 1/8 steel. 💡

i actually though about this as well...but welding it shut and water tight some vents out of the top and an entrance out of the top with a ladder running though it, couple underground all joined by metal tunnels (the big metal culverts you could actual stand up in and walk around.... generator, gas/ diesel supply.... vented out as well.....the vents would travel horizontally for 100 feet or so away from the hide itself....it could work...thing is it would relativly warm in winter and cool in summer

There are YouTub vids and some sites dedicated to this very idea, some offer free plans some sell plans and parts.
Look up also the $50 and Up Underground House

I got to get me one of those motion detector alarms. Could you recommend a brand?

Good to the "slap locks" work. I put them on all my doors last year and wondered if they were really any good

i've used two motion alarms,
chamberlain and MURS.
both work great for what they do.
Chamberlain has upgraded some of it's stuff. i have the model CWA 2000 mine will only take 4 sensors, but my buddy just upgraded his chamberlain system to the "CWA 2000" unit and his takes 8 sensors.

i so watch what it'll do when you are buying one, it should state on the front of the box if it's a 4 or 8 sensor system. of course the unit comes with only 1 receiver, and one sensor, more sensors are bought at an added price.

the range is good on this unit. when the beam is tripped it sends a "BEEP" to the receiver. if you have 4 sensors each are unique by the number of beeps they produce. sensor 1 = BEEP sensor 4 = BEEP BEEP BEEP BEEP.

so when you use this set up with eight senors and you are counting beeps, i think i'd have trouble "was that 5 or 6? or 7 or 8?" etc. because if you miss a beep or come into the room when it's mid beeping, you might get the wrong zone.

this can be over come by having it layered, zone 1 is the front gate, zone 8 is closer to the house so someone would set of 1 then if they continued on that path they would set off zone 8 as well. this gives your their route. if they come thru your gate but pull close to the tree line to get around to the back of your house, they might set off the zone 2 sensor etc. you'll have to decide if this system with 8 sensors is something that will work with you.

the MURS are pricey, but they work great, have a good range.
it's a sensor that uses the Multi Use Radio Service frequencies to send a signal to the receiver. this is sounded by "alert zone 1, alert zone 1" the receiver can be a base unit, or a handheld. if you have two units you can also use them as a more secure walkie talkie system as MURS is not so big in Canada yet, and from what i've heard it will come under some regulation in the next two years.

i have my scanner set with these frequencies, so not only will the sensors trigger the MURS handheld and the scanner, but i could have the handheld with me, and send a message back to the house to anyone listening on the scanner.
my multi band handheld HAM radio also can be set to pick up the frequency and will pick up the senors if they are triggered.

i use the chamberlain to let me know someone has entered the property, this is a short set beam, so i use it on choke points.

the MURS i use for cover longer runs, they have a beam that can cover 80 feet if you are willing to take the time to get it pointed exactly correctly. they have a long transmission distance as well. so i have extras to use on the road if i ever needed warning of people travelling my directions.

i LOVE both systems. they are $$$$ but i've never regretted buying either of them.
i know of a few people using the chamberlain, and it came high recommended to me, and i know more people using MURS, and i've never heard a bad word about them!