diff --git a/dagger/market.nim b/dagger/market.nim
new file mode 100644
index 00000000..9983db79
--- /dev/null
+++ b/dagger/market.nim
@@ -0,0 +1,11 @@
+import pkg/chronos
+import ./contracts/requests
+
+export chronos
+export requests
+
+type
+  Market* = ref object of RootObj
+
+method requestStorage*(market: Market, request: StorageRequest) {.base, async.} =
+  raiseAssert("not implemented")
diff --git a/dagger/purchasing.nim b/dagger/purchasing.nim
new file mode 100644
index 00000000..655a8699
--- /dev/null
+++ b/dagger/purchasing.nim
@@ -0,0 +1,57 @@
+import std/times
+import pkg/stint
+import pkg/chronos
+import pkg/questionable
+import pkg/nimcrypto
+import ./market
+
+export questionable
+
+type
+  Purchasing* = ref object
+    market: Market
+    proofProbability*: UInt256
+    requestExpiryInterval*: UInt256
+  PurchaseRequest* = object
+    duration*: UInt256
+    size*: UInt256
+    contentHash*: array[32, byte]
+    maxPrice*: UInt256
+    proofProbability*: ?UInt256
+    expiry*: ?UInt256
+  Purchase* = ref object
+
+const DefaultProofProbability = 100.u256
+const DefaultRequestExpiryInterval = (10 * 60).u256
+
+proc new*(_: type Purchasing, market: Market): Purchasing =
+  Purchasing(
+    market: market,
+    proofProbability: DefaultProofProbability,
+    requestExpiryInterval: DefaultRequestExpiryInterval
+  )
+
+proc getProofProbability(purchasing: Purchasing, request: PurchaseRequest): UInt256 =
+  request.proofProbability |? purchasing.proofProbability
+
+proc getExpiry(purchasing: Purchasing, request: PurchaseRequest): UInt256 =
+  request.expiry |? (getTime().toUnix().u256 + purchasing.requestExpiryInterval)
+
+proc getNonce(): array[32, byte] =
+  doAssert randomBytes(result) == 32
+
+proc purchase*(purchasing: Purchasing, request: PurchaseRequest): Purchase =
+  let request: StorageRequest = (
+    client: Address.default, # TODO
+    duration: request.duration,
+    size: request.size,
+    contentHash: request.contentHash,
+    proofProbability: purchasing.getProofProbability(request),
+    maxPrice: request.maxPrice,
+    expiry: purchasing.getExpiry(request),
+    nonce: getNonce()
+  )
+  asyncSpawn purchasing.market.requestStorage(request)
+
+proc wait*(purchase: Purchase) {.async.} =
+  discard
diff --git a/tests/dagger/examples.nim b/tests/dagger/examples.nim
index 0e72de5e..7034640f 100644
--- a/tests/dagger/examples.nim
+++ b/tests/dagger/examples.nim
@@ -2,9 +2,11 @@ import std/random
 import std/sequtils
 import pkg/libp2p
 import pkg/nitro
+import pkg/stint
 import pkg/dagger/rng
 import pkg/dagger/stores
 import pkg/dagger/blocktype
+import pkg/dagger/purchasing
 
 proc example*(_: type EthAddress): EthAddress =
   EthPrivateKey.random().toPublicKey.toAddress
@@ -19,6 +21,13 @@ proc example*(_: type UInt48): UInt48 =
   # workaround for https://github.com/nim-lang/Nim/issues/17670
   uint64.rand mod (UInt48.high + 1)
 
+proc example*[T: SomeInteger](_: type T): T =
+  rand(T)
+
+proc example*[T,N](_: type array[N, T]): array[N, T] =
+  for item in result.mitems:
+    item = T.example
+
 proc example*(_: type Wallet): Wallet =
   Wallet.init(EthPrivateKey.random())
 
@@ -53,3 +62,10 @@ proc example*(_: type BlockExcPeerCtx): BlockExcPeerCtx =
 
 proc example*(_: type Cid): Cid =
   Block.example.cid
+
+proc example*(_: type PurchaseRequest): PurchaseRequest =
+  PurchaseRequest(
+    duration: uint16.example.u256,
+    size: uint32.example.u256,
+    contentHash: array[32, byte].example
+  )
diff --git a/tests/dagger/helpers/mockmarket.nim b/tests/dagger/helpers/mockmarket.nim
new file mode 100644
index 00000000..7f618320
--- /dev/null
+++ b/tests/dagger/helpers/mockmarket.nim
@@ -0,0 +1,8 @@
+import pkg/dagger/market
+
+type
+  MockMarket* = ref object of Market
+    requests*: seq[StorageRequest]
+
+method requestStorage*(market: MockMarket, request: StorageRequest) {.async.} =
+  market.requests.add(request)
diff --git a/tests/dagger/testpurchasing.nim b/tests/dagger/testpurchasing.nim
new file mode 100644
index 00000000..01ea9563
--- /dev/null
+++ b/tests/dagger/testpurchasing.nim
@@ -0,0 +1,59 @@
+import std/times
+import pkg/asynctest
+import pkg/chronos
+import pkg/stint
+import pkg/dagger/purchasing
+import ./helpers/mockmarket
+import ./examples
+
+suite "Purchasing":
+
+  var purchasing: Purchasing
+  var market: MockMarket
+  var purchaseRequest: PurchaseRequest
+
+  setup:
+    market = MockMarket.new()
+    purchasing = Purchasing.new(market)
+    purchaseRequest = PurchaseRequest.example
+
+  test "submits a storage request when asked":
+    await purchasing.purchase(purchaseRequest).wait()
+    let storageRequest = market.requests[0]
+    check storageRequest.duration == purchaseRequest.duration
+    check storageRequest.size == purchaseRequest.size
+    check storageRequest.contentHash == purchaseRequest.contentHash
+    check storageRequest.maxPrice == purchaseRequest.maxPrice
+
+  test "has a default value for proof probability":
+    check purchasing.proofProbability != 0.u256
+
+  test "can change default value for proof probability":
+    purchasing.proofProbability = 42.u256
+    await purchasing.purchase(purchaseRequest).wait()
+    check market.requests[0].proofProbability == 42.u256
+
+  test "can override proof probability per request":
+    purchaseRequest.proofProbability = some 42.u256
+    await purchasing.purchase(purchaseRequest).wait()
+    check market.requests[0].proofProbability == 42.u256
+
+  test "has a default value for request expiration interval":
+    check purchasing.requestExpiryInterval != 0.u256
+
+  test "can change default value for request expiration interval":
+    purchasing.requestExpiryInterval = 42.u256
+    let start = getTime().toUnix()
+    await purchasing.purchase(purchaseRequest).wait()
+    check market.requests[0].expiry == (start + 42).u256
+
+  test "can override expiry time per request":
+    let expiry = (getTime().toUnix() + 42).u256
+    purchaseRequest.expiry = some expiry
+    await purchasing.purchase(purchaseRequest).wait()
+    check market.requests[0].expiry == expiry
+
+  test "includes a random nonce in every storage request":
+    await purchasing.purchase(purchaseRequest).wait()
+    await purchasing.purchase(purchaseRequest).wait()
+    check market.requests[0].nonce != market.requests[1].nonce
diff --git a/tests/testDagger.nim b/tests/testDagger.nim
index 37914987..9b7d2ec0 100644
--- a/tests/testDagger.nim
+++ b/tests/testDagger.nim
@@ -5,5 +5,6 @@ import ./dagger/testchunking
 import ./dagger/testmanifest
 import ./dagger/testnode
 import ./dagger/teststorestream
+import ./dagger/testpurchasing
 
 {.warning[UnusedImport]: off.}